diff -r 000000000000 -r 6474c204b198 gfx/layers/apz/src/AsyncPanZoomController.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gfx/layers/apz/src/AsyncPanZoomController.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,2209 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set sw=2 ts=8 et tw=80 : */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <math.h>                       // for fabsf, fabs, atan2
+#include <stdint.h>                     // for uint32_t, uint64_t
+#include <sys/types.h>                  // for int32_t
+#include <algorithm>                    // for max, min
+#include "AnimationCommon.h"            // for ComputedTimingFunction
+#include "AsyncPanZoomController.h"     // for AsyncPanZoomController, etc
+#include "CompositorParent.h"           // for CompositorParent
+#include "FrameMetrics.h"               // for FrameMetrics, etc
+#include "GestureEventListener.h"       // for GestureEventListener
+#include "InputData.h"                  // for MultiTouchInput, etc
+#include "Units.h"                      // for CSSRect, CSSPoint, etc
+#include "UnitTransforms.h"             // for TransformTo
+#include "base/message_loop.h"          // for MessageLoop
+#include "base/task.h"                  // for NewRunnableMethod, etc
+#include "base/tracked.h"               // for FROM_HERE
+#include "gfxPrefs.h"                   // for gfxPrefs
+#include "gfxTypes.h"                   // for gfxFloat
+#include "mozilla/Assertions.h"         // for MOZ_ASSERT, etc
+#include "mozilla/BasicEvents.h"        // for Modifiers, MODIFIER_*
+#include "mozilla/ClearOnShutdown.h"    // for ClearOnShutdown
+#include "mozilla/Constants.h"          // for M_PI
+#include "mozilla/EventForwards.h"      // for nsEventStatus_*
+#include "mozilla/Preferences.h"        // for Preferences
+#include "mozilla/ReentrantMonitor.h"   // for ReentrantMonitorAutoEnter, etc
+#include "mozilla/StaticPtr.h"          // for StaticAutoPtr
+#include "mozilla/TimeStamp.h"          // for TimeDuration, TimeStamp
+#include "mozilla/dom/Touch.h"          // for Touch
+#include "mozilla/gfx/BasePoint.h"      // for BasePoint
+#include "mozilla/gfx/BaseRect.h"       // for BaseRect
+#include "mozilla/gfx/Point.h"          // for Point, RoundedToInt, etc
+#include "mozilla/gfx/Rect.h"           // for RoundedIn
+#include "mozilla/gfx/ScaleFactor.h"    // for ScaleFactor
+#include "mozilla/layers/APZCTreeManager.h"  // for ScrollableLayerGuid
+#include "mozilla/layers/AsyncCompositionManager.h"  // for ViewTransform
+#include "mozilla/layers/Axis.h"        // for AxisX, AxisY, Axis, etc
+#include "mozilla/layers/LayerTransactionParent.h" // for LayerTransactionParent
+#include "mozilla/layers/PCompositorParent.h" // for PCompositorParent
+#include "mozilla/layers/TaskThrottler.h"  // for TaskThrottler
+#include "mozilla/mozalloc.h"           // for operator new, etc
+#include "mozilla/unused.h"             // for unused
+#include "mozilla/FloatingPoint.h"      // for FuzzyEqualsMultiplicative
+#include "nsAlgorithm.h"                // for clamped
+#include "nsAutoPtr.h"                  // for nsRefPtr
+#include "nsCOMPtr.h"                   // for already_AddRefed
+#include "nsDebug.h"                    // for NS_WARNING
+#include "nsIDOMWindowUtils.h"          // for nsIDOMWindowUtils
+#include "nsISupportsImpl.h"            // for MOZ_COUNT_CTOR, etc
+#include "nsMathUtils.h"                // for NS_hypot
+#include "nsPoint.h"                    // for nsIntPoint
+#include "nsStyleConsts.h"
+#include "nsStyleStruct.h"              // for nsTimingFunction
+#include "nsTArray.h"                   // for nsTArray, nsTArray_Impl, etc
+#include "nsThreadUtils.h"              // for NS_IsMainThread
+#include "SharedMemoryBasic.h"          // for SharedMemoryBasic
+
+// #define APZC_ENABLE_RENDERTRACE
+
+#define APZC_LOG(...)
+// #define APZC_LOG(...) printf_stderr("APZC: " __VA_ARGS__)
+#define APZC_LOG_FM(fm, prefix, ...) \
+  APZC_LOG(prefix ":" \
+           " i=(%ld %lld) cb=(%d %d %d %d) rcs=(%.3f %.3f) dp=(%.3f %.3f %.3f %.3f) dpm=(%.3f %.3f %.3f %.3f) um=%d " \
+           "v=(%.3f %.3f %.3f %.3f) s=(%.3f %.3f) sr=(%.3f %.3f %.3f %.3f) z=(%.3f %.3f %.3f %.3f) u=(%d %lu)\n", \
+           __VA_ARGS__, \
+           fm.mPresShellId, fm.GetScrollId(), \
+           fm.mCompositionBounds.x, fm.mCompositionBounds.y, fm.mCompositionBounds.width, fm.mCompositionBounds.height, \
+           fm.GetRootCompositionSize().width, fm.GetRootCompositionSize().height, \
+           fm.mDisplayPort.x, fm.mDisplayPort.y, fm.mDisplayPort.width, fm.mDisplayPort.height, \
+           fm.GetDisplayPortMargins().top, fm.GetDisplayPortMargins().right, fm.GetDisplayPortMargins().bottom, fm.GetDisplayPortMargins().left, \
+           fm.GetUseDisplayPortMargins() ? 1 : 0, \
+           fm.mViewport.x, fm.mViewport.y, fm.mViewport.width, fm.mViewport.height, \
+           fm.GetScrollOffset().x, fm.GetScrollOffset().y, \
+           fm.mScrollableRect.x, fm.mScrollableRect.y, fm.mScrollableRect.width, fm.mScrollableRect.height, \
+           fm.mDevPixelsPerCSSPixel.scale, fm.mResolution.scale, fm.mCumulativeResolution.scale, fm.GetZoom().scale, \
+           fm.GetScrollOffsetUpdated(), fm.GetScrollGeneration()); \
+
+// Static helper functions
+namespace {
+
+int32_t
+WidgetModifiersToDOMModifiers(mozilla::Modifiers aModifiers)
+{
+  int32_t result = 0;
+  if (aModifiers & mozilla::MODIFIER_SHIFT) {
+    result |= nsIDOMWindowUtils::MODIFIER_SHIFT;
+  }
+  if (aModifiers & mozilla::MODIFIER_CONTROL) {
+    result |= nsIDOMWindowUtils::MODIFIER_CONTROL;
+  }
+  if (aModifiers & mozilla::MODIFIER_ALT) {
+    result |= nsIDOMWindowUtils::MODIFIER_ALT;
+  }
+  if (aModifiers & mozilla::MODIFIER_META) {
+    result |= nsIDOMWindowUtils::MODIFIER_META;
+  }
+  if (aModifiers & mozilla::MODIFIER_ALTGRAPH) {
+    result |= nsIDOMWindowUtils::MODIFIER_ALTGRAPH;
+  }
+  if (aModifiers & mozilla::MODIFIER_CAPSLOCK) {
+    result |= nsIDOMWindowUtils::MODIFIER_CAPSLOCK;
+  }
+  if (aModifiers & mozilla::MODIFIER_FN) {
+    result |= nsIDOMWindowUtils::MODIFIER_FN;
+  }
+  if (aModifiers & mozilla::MODIFIER_NUMLOCK) {
+    result |= nsIDOMWindowUtils::MODIFIER_NUMLOCK;
+  }
+  if (aModifiers & mozilla::MODIFIER_SCROLLLOCK) {
+    result |= nsIDOMWindowUtils::MODIFIER_SCROLLLOCK;
+  }
+  if (aModifiers & mozilla::MODIFIER_SYMBOLLOCK) {
+    result |= nsIDOMWindowUtils::MODIFIER_SYMBOLLOCK;
+  }
+  if (aModifiers & mozilla::MODIFIER_OS) {
+    result |= nsIDOMWindowUtils::MODIFIER_OS;
+  }
+  return result;
+}
+
+}
+
+using namespace mozilla::css;
+
+namespace mozilla {
+namespace layers {
+
+typedef mozilla::layers::AllowedTouchBehavior AllowedTouchBehavior;
+typedef GeckoContentController::APZStateChange APZStateChange;
+
+/*
+ * The following prefs are used to control the behaviour of the APZC.
+ * The default values are provided in gfxPrefs.h.
+ *
+ * "apz.allow-checkerboarding"
+ * Pref that allows or disallows checkerboarding
+ *
+ * "apz.asyncscroll.throttle"
+ * The time period in ms that throttles mozbrowserasyncscroll event.
+ *
+ * "apz.asyncscroll.timeout"
+ * The timeout in ms for mAsyncScrollTimeoutTask delay task.
+ *
+ * "apz.axis_lock_mode"
+ * The preferred axis locking style. See AxisLockMode for possible values.
+ *
+ * "apz.content_response_timeout"
+ * Amount of time before we timeout response from content. For example, if
+ * content is being unruly/slow and we don't get a response back within this
+ * time, we will just pretend that content did not preventDefault any touch
+ * events we dispatched to it.
+ *
+ * "apz.cross_slide_enabled"
+ * Pref that enables integration with the Metro "cross-slide" gesture.
+ *
+ * "apz.enlarge_displayport_when_clipped"
+ * Pref that enables enlarging of the displayport along one axis when the
+ * generated displayport's size is beyond that of the scrollable rect on the
+ * opposite axis.
+ *
+ * "apz.fling_friction"
+ * Amount of friction applied during flings.
+ *
+ * "apz.fling_repaint_interval"
+ * Maximum amount of time flinging before sending a viewport change. This will
+ * asynchronously repaint the page.
+ *
+ * "apz.fling_stopped_threshold"
+ * When flinging, if the velocity goes below this number, we just stop the
+ * animation completely. This is to prevent asymptotically approaching 0
+ * velocity and rerendering unnecessarily.
+ *
+ * "apz.max_velocity_inches_per_ms"
+ * Maximum velocity in inches per millisecond.  Velocity will be capped at this
+ * value if a faster fling occurs.  Negative values indicate unlimited velocity.
+ *
+ * "apz.max_velocity_queue_size"
+ * Maximum size of velocity queue. The queue contains last N velocity records.
+ * On touch end we calculate the average velocity in order to compensate
+ * touch/mouse drivers misbehaviour.
+ *
+ * "apz.min_skate_speed"
+ * Minimum amount of speed along an axis before we switch to "skate" multipliers
+ * rather than using the "stationary" multipliers.
+ *
+ * "apz.num_paint_duration_samples"
+ * Number of samples to store of how long it took to paint after the previous
+ * requests.
+ *
+ * "apz.pan_repaint_interval"
+ * Maximum amount of time while panning before sending a viewport change. This
+ * will asynchronously repaint the page. It is also forced when panning stops.
+ *
+ * "apz.touch_start_tolerance"
+ * Constant describing the tolerance in distance we use, multiplied by the
+ * device DPI, before we start panning the screen. This is to prevent us from
+ * accidentally processing taps as touch moves, and from very short/accidental
+ * touches moving the screen.
+ *
+ * "apz.use_paint_duration"
+ * Whether or not to use the estimated paint duration as a factor when projecting
+ * the displayport in the direction of scrolling. If this value is set to false,
+ * a constant 50ms paint time is used; the projection can be scaled as desired
+ * using the apz.velocity_bias pref below.
+ *
+ * "apz.velocity_bias"
+ * How much to adjust the displayport in the direction of scrolling. This value
+ * is multiplied by the velocity and added to the displayport offset.
+ *
+ * "apz.x_skate_size_multiplier", "apz.y_skate_size_multiplier"
+ * The multiplier we apply to the displayport size if it is skating (current
+ * velocity is above apz.min_skate_speed). We prefer to increase the size of the
+ * Y axis because it is more natural in the case that a user is reading a page
+ * that scrolls up/down. Note that one, both or neither of these may be used
+ * at any instant.
+ * In general we want apz.[xy]_skate_size_multiplier to be smaller than the corresponding
+ * stationary size multiplier because when panning fast we would like to paint
+ * less and get faster, more predictable paint times. When panning slowly we
+ * can afford to paint more even though it's slower.
+ *
+ * "apz.x_stationary_size_multiplier", "apz.y_stationary_size_multiplier"
+ * The multiplier we apply to the displayport size if it is not skating (see
+ * documentation for the skate size multipliers above).
+ */
+
+/**
+ * Default touch behavior (is used when not touch behavior is set).
+ */
+static const uint32_t DefaultTouchBehavior = AllowedTouchBehavior::VERTICAL_PAN |
+                                             AllowedTouchBehavior::HORIZONTAL_PAN |
+                                             AllowedTouchBehavior::PINCH_ZOOM |
+                                             AllowedTouchBehavior::DOUBLE_TAP_ZOOM;
+
+/**
+ * Angle from axis within which we stay axis-locked
+ */
+static const double AXIS_LOCK_ANGLE = M_PI / 6.0; // 30 degrees
+
+/**
+ * The distance in inches the user must pan before axis lock can be broken
+ */
+static const float AXIS_BREAKOUT_THRESHOLD = 1.0f/32.0f;
+
+/**
+ * The angle at which axis lock can be broken
+ */
+static const double AXIS_BREAKOUT_ANGLE = M_PI / 8.0; // 22.5 degrees
+
+/**
+ * Angle from axis to the line drawn by pan move.
+ * If angle is less than this value we can assume that panning
+ * can be done in allowed direction (horizontal or vertical).
+ * Currently used only for touch-action css property stuff and was
+ * added to keep behavior consistent with IE.
+ */
+static const double ALLOWED_DIRECT_PAN_ANGLE = M_PI / 3.0; // 60 degrees
+
+/**
+ * Duration of a zoom to animation.
+ */
+static const TimeDuration ZOOM_TO_DURATION = TimeDuration::FromSeconds(0.25);
+
+/**
+ * Computed time function used for sampling frames of a zoom to animation.
+ */
+StaticAutoPtr<ComputedTimingFunction> gComputedTimingFunction;
+
+/**
+ * Maximum zoom amount, always used, even if a page asks for higher.
+ */
+static const CSSToScreenScale MAX_ZOOM(8.0f);
+
+/**
+ * Minimum zoom amount, always used, even if a page asks for lower.
+ */
+static const CSSToScreenScale MIN_ZOOM(0.125f);
+
+/**
+ * Is aAngle within the given threshold of the horizontal axis?
+ * @param aAngle an angle in radians in the range [0, pi]
+ * @param aThreshold an angle in radians in the range [0, pi/2]
+ */
+static bool IsCloseToHorizontal(float aAngle, float aThreshold)
+{
+  return (aAngle < aThreshold || aAngle > (M_PI - aThreshold));
+}
+
+// As above, but for the vertical axis.
+static bool IsCloseToVertical(float aAngle, float aThreshold)
+{
+  return (fabs(aAngle - (M_PI / 2)) < aThreshold);
+}
+
+template <typename Units>
+static bool IsZero(const gfx::PointTyped<Units>& aPoint)
+{
+  return FuzzyEqualsMultiplicative(aPoint.x, 0.0f)
+      && FuzzyEqualsMultiplicative(aPoint.y, 0.0f);
+}
+
+static inline void LogRendertraceRect(const ScrollableLayerGuid& aGuid, const char* aDesc, const char* aColor, const CSSRect& aRect)
+{
+#ifdef APZC_ENABLE_RENDERTRACE
+  static const TimeStamp sRenderStart = TimeStamp::Now();
+  TimeDuration delta = TimeStamp::Now() - sRenderStart;
+  printf_stderr("(%llu,%lu,%llu)%s RENDERTRACE %f rect %s %f %f %f %f\n",
+    aGuid.mLayersId, aGuid.mPresShellId, aGuid.GetScrollId(),
+    aDesc, delta.ToMilliseconds(), aColor,
+    aRect.x, aRect.y, aRect.width, aRect.height);
+#endif
+}
+
+static TimeStamp sFrameTime;
+
+// Counter used to give each APZC a unique id
+static uint32_t sAsyncPanZoomControllerCount = 0;
+
+static TimeStamp
+GetFrameTime() {
+  if (sFrameTime.IsNull()) {
+    return TimeStamp::Now();
+  }
+  return sFrameTime;
+}
+
+class FlingAnimation: public AsyncPanZoomAnimation {
+public:
+  FlingAnimation(AsyncPanZoomController& aApzc)
+    : AsyncPanZoomAnimation(TimeDuration::FromMilliseconds(gfxPrefs::APZFlingRepaintInterval()))
+    , mApzc(aApzc)
+  {}
+  /**
+   * Advances a fling by an interpolated amount based on the passed in |aDelta|.
+   * This should be called whenever sampling the content transform for this
+   * frame. Returns true if the fling animation should be advanced by one frame,
+   * or false if there is no fling or the fling has ended.
+   */
+  virtual bool Sample(FrameMetrics& aFrameMetrics,
+                      const TimeDuration& aDelta);
+
+private:
+  AsyncPanZoomController& mApzc;
+};
+
+class ZoomAnimation: public AsyncPanZoomAnimation {
+public:
+  ZoomAnimation(CSSPoint aStartOffset, CSSToScreenScale aStartZoom,
+                CSSPoint aEndOffset, CSSToScreenScale aEndZoom)
+    : mStartOffset(aStartOffset)
+    , mStartZoom(aStartZoom)
+    , mEndOffset(aEndOffset)
+    , mEndZoom(aEndZoom)
+  {}
+
+  virtual bool Sample(FrameMetrics& aFrameMetrics,
+                      const TimeDuration& aDelta);
+
+private:
+  TimeDuration mDuration;
+
+  // Old metrics from before we started a zoom animation. This is only valid
+  // when we are in the "ANIMATED_ZOOM" state. This is used so that we can
+  // interpolate between the start and end frames. We only use the
+  // |mViewportScrollOffset| and |mResolution| fields on this.
+  CSSPoint mStartOffset;
+  CSSToScreenScale mStartZoom;
+
+  // Target metrics for a zoom to animation. This is only valid when we are in
+  // the "ANIMATED_ZOOM" state. We only use the |mViewportScrollOffset| and
+  // |mResolution| fields on this.
+  CSSPoint mEndOffset;
+  CSSToScreenScale mEndZoom;
+};
+
+void
+AsyncPanZoomController::SetFrameTime(const TimeStamp& aTime) {
+  sFrameTime = aTime;
+}
+
+/*static*/ void
+AsyncPanZoomController::InitializeGlobalState()
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  static bool sInitialized = false;
+  if (sInitialized)
+    return;
+  sInitialized = true;
+
+  gComputedTimingFunction = new ComputedTimingFunction();
+  gComputedTimingFunction->Init(
+    nsTimingFunction(NS_STYLE_TRANSITION_TIMING_FUNCTION_EASE));
+  ClearOnShutdown(&gComputedTimingFunction);
+}
+
+AsyncPanZoomController::AsyncPanZoomController(uint64_t aLayersId,
+                                               APZCTreeManager* aTreeManager,
+                                               GeckoContentController* aGeckoContentController,
+                                               GestureBehavior aGestures)
+  :  mLayersId(aLayersId),
+     mCrossProcessCompositorParent(nullptr),
+     mPaintThrottler(GetFrameTime()),
+     mGeckoContentController(aGeckoContentController),
+     mRefPtrMonitor("RefPtrMonitor"),
+     mMonitor("AsyncPanZoomController"),
+     mTouchActionPropertyEnabled(gfxPrefs::TouchActionEnabled()),
+     mContentResponseTimeoutTask(nullptr),
+     mX(MOZ_THIS_IN_INITIALIZER_LIST()),
+     mY(MOZ_THIS_IN_INITIALIZER_LIST()),
+     mPanDirRestricted(false),
+     mZoomConstraints(false, false, MIN_ZOOM, MAX_ZOOM),
+     mLastSampleTime(GetFrameTime()),
+     mState(NOTHING),
+     mLastAsyncScrollTime(GetFrameTime()),
+     mLastAsyncScrollOffset(0, 0),
+     mCurrentAsyncScrollOffset(0, 0),
+     mAsyncScrollTimeoutTask(nullptr),
+     mHandlingTouchQueue(false),
+     mTreeManager(aTreeManager),
+     mScrollParentId(FrameMetrics::NULL_SCROLL_ID),
+     mAPZCId(sAsyncPanZoomControllerCount++),
+     mSharedFrameMetricsBuffer(nullptr),
+     mSharedLock(nullptr)
+{
+  MOZ_COUNT_CTOR(AsyncPanZoomController);
+
+  if (aGestures == USE_GESTURE_DETECTOR) {
+    mGestureEventListener = new GestureEventListener(this);
+  }
+}
+
+AsyncPanZoomController::~AsyncPanZoomController() {
+
+  PCompositorParent* compositor =
+    (mCrossProcessCompositorParent ? mCrossProcessCompositorParent : mCompositorParent.get());
+
+  // Only send the release message if the SharedFrameMetrics has been created.
+  if (compositor && mSharedFrameMetricsBuffer) {
+    unused << compositor->SendReleaseSharedCompositorFrameMetrics(mFrameMetrics.GetScrollId(), mAPZCId);
+  }
+
+  delete mSharedFrameMetricsBuffer;
+  delete mSharedLock;
+
+  MOZ_COUNT_DTOR(AsyncPanZoomController);
+}
+
+already_AddRefed<GeckoContentController>
+AsyncPanZoomController::GetGeckoContentController() {
+  MonitorAutoLock lock(mRefPtrMonitor);
+  nsRefPtr<GeckoContentController> controller = mGeckoContentController;
+  return controller.forget();
+}
+
+already_AddRefed<GestureEventListener>
+AsyncPanZoomController::GetGestureEventListener() {
+  MonitorAutoLock lock(mRefPtrMonitor);
+  nsRefPtr<GestureEventListener> listener = mGestureEventListener;
+  return listener.forget();
+}
+
+void
+AsyncPanZoomController::Destroy()
+{
+  { // scope the lock
+    MonitorAutoLock lock(mRefPtrMonitor);
+    mGeckoContentController = nullptr;
+    mGestureEventListener = nullptr;
+  }
+  mPrevSibling = nullptr;
+  mLastChild = nullptr;
+  mParent = nullptr;
+  mTreeManager = nullptr;
+}
+
+bool
+AsyncPanZoomController::IsDestroyed()
+{
+  return mTreeManager == nullptr;
+}
+
+/* static */float
+AsyncPanZoomController::GetTouchStartTolerance()
+{
+  return (gfxPrefs::APZTouchStartTolerance() * APZCTreeManager::GetDPI());
+}
+
+/* static */AsyncPanZoomController::AxisLockMode AsyncPanZoomController::GetAxisLockMode()
+{
+  return static_cast<AxisLockMode>(gfxPrefs::APZAxisLockMode());
+}
+
+nsEventStatus AsyncPanZoomController::ReceiveInputEvent(const InputData& aEvent) {
+  if (aEvent.mInputType == MULTITOUCH_INPUT &&
+      aEvent.AsMultiTouchInput().mType == MultiTouchInput::MULTITOUCH_START) {
+    // Starting a new touch block, clear old touch block state.
+    mTouchBlockState = TouchBlockState();
+  }
+
+  // If we may have touch listeners and touch action property is enabled, we
+  // enable the machinery that allows touch listeners to preventDefault any touch inputs
+  // and also waits for the allowed touch behavior values to be received from the outside.
+  // This should not happen unless there are actually touch listeners and touch-action property
+  // enable as it introduces potentially unbounded lag because it causes a round-trip through
+  // content.  Usually, if content is responding in a timely fashion, this only introduces a
+  // nearly constant few hundred ms of lag.
+  if (mFrameMetrics.mMayHaveTouchListeners && aEvent.mInputType == MULTITOUCH_INPUT &&
+      (mState == NOTHING || mState == TOUCHING || IsPanningState(mState))) {
+    const MultiTouchInput& multiTouchInput = aEvent.AsMultiTouchInput();
+    if (multiTouchInput.mType == MultiTouchInput::MULTITOUCH_START) {
+      SetState(WAITING_CONTENT_RESPONSE);
+    }
+  }
+
+  if (mState == WAITING_CONTENT_RESPONSE || mHandlingTouchQueue) {
+    if (aEvent.mInputType == MULTITOUCH_INPUT) {
+      const MultiTouchInput& multiTouchInput = aEvent.AsMultiTouchInput();
+      mTouchQueue.AppendElement(multiTouchInput);
+
+      SetContentResponseTimer();
+    }
+    return nsEventStatus_eIgnore;
+  }
+
+  return HandleInputEvent(aEvent);
+}
+
+nsEventStatus AsyncPanZoomController::HandleInputEvent(const InputData& aEvent) {
+  nsEventStatus rv = nsEventStatus_eIgnore;
+
+  switch (aEvent.mInputType) {
+  case MULTITOUCH_INPUT: {
+    const MultiTouchInput& multiTouchInput = aEvent.AsMultiTouchInput();
+
+    nsRefPtr<GestureEventListener> listener = GetGestureEventListener();
+    if (listener) {
+      rv = listener->HandleInputEvent(multiTouchInput);
+      if (rv == nsEventStatus_eConsumeNoDefault) {
+        return rv;
+      }
+    }
+
+    switch (multiTouchInput.mType) {
+      case MultiTouchInput::MULTITOUCH_START: rv = OnTouchStart(multiTouchInput); break;
+      case MultiTouchInput::MULTITOUCH_MOVE: rv = OnTouchMove(multiTouchInput); break;
+      case MultiTouchInput::MULTITOUCH_END: rv = OnTouchEnd(multiTouchInput); break;
+      case MultiTouchInput::MULTITOUCH_CANCEL: rv = OnTouchCancel(multiTouchInput); break;
+      default: NS_WARNING("Unhandled multitouch"); break;
+    }
+    break;
+  }
+  default: NS_WARNING("Unhandled input event"); break;
+  }
+
+  mLastEventTime = aEvent.mTime;
+  return rv;
+}
+
+nsEventStatus AsyncPanZoomController::HandleGestureEvent(const InputData& aEvent)
+{
+  nsEventStatus rv = nsEventStatus_eIgnore;
+
+  switch (aEvent.mInputType) {
+  case PINCHGESTURE_INPUT: {
+    const PinchGestureInput& pinchGestureInput = aEvent.AsPinchGestureInput();
+    switch (pinchGestureInput.mType) {
+      case PinchGestureInput::PINCHGESTURE_START: rv = OnScaleBegin(pinchGestureInput); break;
+      case PinchGestureInput::PINCHGESTURE_SCALE: rv = OnScale(pinchGestureInput); break;
+      case PinchGestureInput::PINCHGESTURE_END: rv = OnScaleEnd(pinchGestureInput); break;
+      default: NS_WARNING("Unhandled pinch gesture"); break;
+    }
+    break;
+  }
+  case TAPGESTURE_INPUT: {
+    const TapGestureInput& tapGestureInput = aEvent.AsTapGestureInput();
+    switch (tapGestureInput.mType) {
+      case TapGestureInput::TAPGESTURE_LONG: rv = OnLongPress(tapGestureInput); break;
+      case TapGestureInput::TAPGESTURE_LONG_UP: rv = OnLongPressUp(tapGestureInput); break;
+      case TapGestureInput::TAPGESTURE_UP: rv = OnSingleTapUp(tapGestureInput); break;
+      case TapGestureInput::TAPGESTURE_CONFIRMED: rv = OnSingleTapConfirmed(tapGestureInput); break;
+      case TapGestureInput::TAPGESTURE_DOUBLE: rv = OnDoubleTap(tapGestureInput); break;
+      case TapGestureInput::TAPGESTURE_CANCEL: rv = OnCancelTap(tapGestureInput); break;
+      default: NS_WARNING("Unhandled tap gesture"); break;
+    }
+    break;
+  }
+  default: NS_WARNING("Unhandled input event"); break;
+  }
+
+  mLastEventTime = aEvent.mTime;
+  return rv;
+}
+
+nsEventStatus AsyncPanZoomController::OnTouchStart(const MultiTouchInput& aEvent) {
+  APZC_LOG("%p got a touch-start in state %d\n", this, mState);
+  mPanDirRestricted = false;
+  ScreenIntPoint point = GetFirstTouchScreenPoint(aEvent);
+
+  switch (mState) {
+    case ANIMATING_ZOOM:
+      // We just interrupted a double-tap animation, so force a redraw in case
+      // this touchstart is just a tap that doesn't end up triggering a redraw.
+      {
+        ReentrantMonitorAutoEnter lock(mMonitor);
+        RequestContentRepaint();
+        ScheduleComposite();
+        UpdateSharedCompositorFrameMetrics();
+      }
+      // Fall through.
+    case FLING:
+      CancelAnimation();
+      // Fall through.
+    case NOTHING: {
+      mX.StartTouch(point.x);
+      mY.StartTouch(point.y);
+      APZCTreeManager* treeManagerLocal = mTreeManager;
+      nsRefPtr<GeckoContentController> controller = GetGeckoContentController();
+      if (treeManagerLocal && controller) {
+        bool touchCanBePan = treeManagerLocal->CanBePanned(this);
+        controller->NotifyAPZStateChange(
+            GetGuid(), APZStateChange::StartTouch, touchCanBePan);
+      }
+      SetState(TOUCHING);
+      break;
+    }
+    case TOUCHING:
+    case PANNING:
+    case PANNING_LOCKED_X:
+    case PANNING_LOCKED_Y:
+    case CROSS_SLIDING_X:
+    case CROSS_SLIDING_Y:
+    case PINCHING:
+    case WAITING_CONTENT_RESPONSE:
+      NS_WARNING("Received impossible touch in OnTouchStart");
+      break;
+    default:
+      NS_WARNING("Unhandled case in OnTouchStart");
+      break;
+  }
+
+  return nsEventStatus_eConsumeNoDefault;
+}
+
+nsEventStatus AsyncPanZoomController::OnTouchMove(const MultiTouchInput& aEvent) {
+  APZC_LOG("%p got a touch-move in state %d\n", this, mState);
+  switch (mState) {
+    case FLING:
+    case NOTHING:
+    case ANIMATING_ZOOM:
+      // May happen if the user double-taps and drags without lifting after the
+      // second tap. Ignore the move if this happens.
+      return nsEventStatus_eIgnore;
+
+    case CROSS_SLIDING_X:
+    case CROSS_SLIDING_Y:
+      // While cross-sliding, we don't want to consume any touchmove events for
+      // panning or zooming, and let the caller handle them instead.
+      return nsEventStatus_eIgnore;
+
+    case TOUCHING: {
+      float panThreshold = GetTouchStartTolerance();
+      UpdateWithTouchAtDevicePoint(aEvent);
+
+      if (PanDistance() < panThreshold) {
+        return nsEventStatus_eIgnore;
+      }
+
+      if (mTouchActionPropertyEnabled &&
+          (GetTouchBehavior(0) & AllowedTouchBehavior::VERTICAL_PAN) &&
+          (GetTouchBehavior(0) & AllowedTouchBehavior::HORIZONTAL_PAN)) {
+        // User tries to trigger a touch behavior. If allowed touch behavior is vertical pan
+        // + horizontal pan (touch-action value is equal to AUTO) we can return ConsumeNoDefault
+        // status immediately to trigger cancel event further. It should happen independent of
+        // the parent type (whether it is scrolling or not).
+        StartPanning(aEvent);
+        return nsEventStatus_eConsumeNoDefault;
+      }
+
+      return StartPanning(aEvent);
+    }
+
+    case PANNING:
+    case PANNING_LOCKED_X:
+    case PANNING_LOCKED_Y:
+      TrackTouch(aEvent);
+      return nsEventStatus_eConsumeNoDefault;
+
+    case PINCHING:
+      // The scale gesture listener should have handled this.
+      NS_WARNING("Gesture listener should have handled pinching in OnTouchMove.");
+      return nsEventStatus_eIgnore;
+
+    case WAITING_CONTENT_RESPONSE:
+      NS_WARNING("Received impossible touch in OnTouchMove");
+      break;
+  }
+
+  return nsEventStatus_eConsumeNoDefault;
+}
+
+nsEventStatus AsyncPanZoomController::OnTouchEnd(const MultiTouchInput& aEvent) {
+  APZC_LOG("%p got a touch-end in state %d\n", this, mState);
+
+  OnTouchEndOrCancel();
+
+  // In case no touch behavior triggered previously we can avoid sending
+  // scroll events or requesting content repaint. This condition is added
+  // to make tests consistent - in case touch-action is NONE (and therefore
+  // no pans/zooms can be performed) we expected neither scroll or repaint
+  // events.
+  if (mState != NOTHING) {
+    ReentrantMonitorAutoEnter lock(mMonitor);
+    SendAsyncScrollEvent();
+  }
+
+  switch (mState) {
+  case FLING:
+    // Should never happen.
+    NS_WARNING("Received impossible touch end in OnTouchEnd.");
+    // Fall through.
+  case ANIMATING_ZOOM:
+  case NOTHING:
+    // May happen if the user double-taps and drags without lifting after the
+    // second tap. Ignore if this happens.
+    return nsEventStatus_eIgnore;
+
+  case TOUCHING:
+  case CROSS_SLIDING_X:
+  case CROSS_SLIDING_Y:
+    SetState(NOTHING);
+    return nsEventStatus_eIgnore;
+
+  case PANNING:
+  case PANNING_LOCKED_X:
+  case PANNING_LOCKED_Y:
+    {
+      // Make a local copy of the tree manager pointer and check if it's not
+      // null before calling FlushRepaintsForOverscrollHandoffChain().
+      // This is necessary because Destroy(), which nulls out mTreeManager,
+      // could be called concurrently.
+      APZCTreeManager* treeManagerLocal = mTreeManager;
+      if (treeManagerLocal) {
+        if (!treeManagerLocal->FlushRepaintsForOverscrollHandoffChain()) {
+          NS_WARNING("Overscroll handoff chain was empty during panning! This should not be the case.");
+          // Graceful handling of error condition
+          FlushRepaintForOverscrollHandoff();
+        }
+      }
+    }
+    mX.EndTouch();
+    mY.EndTouch();
+    SetState(FLING);
+    StartAnimation(new FlingAnimation(*this));
+    return nsEventStatus_eConsumeNoDefault;
+
+  case PINCHING:
+    SetState(NOTHING);
+    // Scale gesture listener should have handled this.
+    NS_WARNING("Gesture listener should have handled pinching in OnTouchEnd.");
+    return nsEventStatus_eIgnore;
+
+  case WAITING_CONTENT_RESPONSE:
+    NS_WARNING("Received impossible touch in OnTouchEnd");
+    break;
+  }
+
+  return nsEventStatus_eConsumeNoDefault;
+}
+
+nsEventStatus AsyncPanZoomController::OnTouchCancel(const MultiTouchInput& aEvent) {
+  APZC_LOG("%p got a touch-cancel in state %d\n", this, mState);
+  OnTouchEndOrCancel();
+  SetState(NOTHING);
+  return nsEventStatus_eConsumeNoDefault;
+}
+
+nsEventStatus AsyncPanZoomController::OnScaleBegin(const PinchGestureInput& aEvent) {
+  APZC_LOG("%p got a scale-begin in state %d\n", this, mState);
+
+  if (!TouchActionAllowPinchZoom()) {
+    return nsEventStatus_eIgnore;
+  }
+
+  if (!mZoomConstraints.mAllowZoom) {
+    return nsEventStatus_eConsumeNoDefault;
+  }
+
+  SetState(PINCHING);
+  mLastZoomFocus = ToParentLayerCoords(aEvent.mFocusPoint) - mFrameMetrics.mCompositionBounds.TopLeft();
+
+  return nsEventStatus_eConsumeNoDefault;
+}
+
+nsEventStatus AsyncPanZoomController::OnScale(const PinchGestureInput& aEvent) {
+  APZC_LOG("%p got a scale in state %d\n", this, mState);
+  if (mState != PINCHING) {
+    return nsEventStatus_eConsumeNoDefault;
+  }
+
+  float prevSpan = aEvent.mPreviousSpan;
+  if (fabsf(prevSpan) <= EPSILON || fabsf(aEvent.mCurrentSpan) <= EPSILON) {
+    // We're still handling it; we've just decided to throw this event away.
+    return nsEventStatus_eConsumeNoDefault;
+  }
+
+  float spanRatio = aEvent.mCurrentSpan / aEvent.mPreviousSpan;
+
+  {
+    ReentrantMonitorAutoEnter lock(mMonitor);
+
+    CSSToParentLayerScale userZoom = mFrameMetrics.GetZoomToParent();
+    ParentLayerPoint focusPoint = ToParentLayerCoords(aEvent.mFocusPoint) - mFrameMetrics.mCompositionBounds.TopLeft();
+    CSSPoint cssFocusPoint = focusPoint / userZoom;
+
+    CSSPoint focusChange = (mLastZoomFocus - focusPoint) / userZoom;
+    // If displacing by the change in focus point will take us off page bounds,
+    // then reduce the displacement such that it doesn't.
+    if (mX.DisplacementWillOverscroll(focusChange.x) != Axis::OVERSCROLL_NONE) {
+      focusChange.x -= mX.DisplacementWillOverscrollAmount(focusChange.x);
+    }
+    if (mY.DisplacementWillOverscroll(focusChange.y) != Axis::OVERSCROLL_NONE) {
+      focusChange.y -= mY.DisplacementWillOverscrollAmount(focusChange.y);
+    }
+    ScrollBy(focusChange);
+
+    // When we zoom in with focus, we can zoom too much towards the boundaries
+    // that we actually go over them. These are the needed displacements along
+    // either axis such that we don't overscroll the boundaries when zooming.
+    CSSPoint neededDisplacement;
+
+    CSSToParentLayerScale realMinZoom = mZoomConstraints.mMinZoom * mFrameMetrics.mTransformScale;
+    CSSToParentLayerScale realMaxZoom = mZoomConstraints.mMaxZoom * mFrameMetrics.mTransformScale;
+    realMinZoom.scale = std::max(realMinZoom.scale,
+                                 mFrameMetrics.mCompositionBounds.width / mFrameMetrics.mScrollableRect.width);
+    realMinZoom.scale = std::max(realMinZoom.scale,
+                                 mFrameMetrics.mCompositionBounds.height / mFrameMetrics.mScrollableRect.height);
+    if (realMaxZoom < realMinZoom) {
+      realMaxZoom = realMinZoom;
+    }
+
+    bool doScale = (spanRatio > 1.0 && userZoom < realMaxZoom) ||
+                   (spanRatio < 1.0 && userZoom > realMinZoom);
+
+    if (doScale) {
+      spanRatio = clamped(spanRatio,
+                          realMinZoom.scale / userZoom.scale,
+                          realMaxZoom.scale / userZoom.scale);
+
+      // Note that the spanRatio here should never put us into OVERSCROLL_BOTH because
+      // up above we clamped it.
+      neededDisplacement.x = -mX.ScaleWillOverscrollAmount(spanRatio, cssFocusPoint.x);
+      neededDisplacement.y = -mY.ScaleWillOverscrollAmount(spanRatio, cssFocusPoint.y);
+
+      ScaleWithFocus(spanRatio, cssFocusPoint);
+
+      if (neededDisplacement != CSSPoint()) {
+        ScrollBy(neededDisplacement);
+      }
+
+      ScheduleComposite();
+      // We don't want to redraw on every scale, so don't use
+      // RequestContentRepaint()
+      UpdateSharedCompositorFrameMetrics();
+    }
+
+    mLastZoomFocus = focusPoint;
+  }
+
+  return nsEventStatus_eConsumeNoDefault;
+}
+
+nsEventStatus AsyncPanZoomController::OnScaleEnd(const PinchGestureInput& aEvent) {
+  APZC_LOG("%p got a scale-end in state %d\n", this, mState);
+
+  SetState(NOTHING);
+
+  {
+    ReentrantMonitorAutoEnter lock(mMonitor);
+    ScheduleComposite();
+    RequestContentRepaint();
+    UpdateSharedCompositorFrameMetrics();
+  }
+
+  return nsEventStatus_eConsumeNoDefault;
+}
+
+bool
+AsyncPanZoomController::ConvertToGecko(const ScreenPoint& aPoint, CSSPoint* aOut)
+{
+  APZCTreeManager* treeManagerLocal = mTreeManager;
+  if (treeManagerLocal) {
+    gfx3DMatrix transformToApzc;
+    gfx3DMatrix transformToGecko;
+    treeManagerLocal->GetInputTransforms(this, transformToApzc, transformToGecko);
+    gfxPoint result = transformToGecko.Transform(gfxPoint(aPoint.x, aPoint.y));
+    // NOTE: This isn't *quite* LayoutDevicePoint, we just don't have a name
+    // for this coordinate space and it maps the closest to LayoutDevicePoint.
+    LayoutDevicePoint layoutPoint = LayoutDevicePoint(result.x, result.y);
+    { // scoped lock to access mFrameMetrics
+      ReentrantMonitorAutoEnter lock(mMonitor);
+      *aOut = layoutPoint / mFrameMetrics.mDevPixelsPerCSSPixel;
+    }
+    return true;
+  }
+  return false;
+}
+
+nsEventStatus AsyncPanZoomController::OnLongPress(const TapGestureInput& aEvent) {
+  APZC_LOG("%p got a long-press in state %d\n", this, mState);
+  nsRefPtr<GeckoContentController> controller = GetGeckoContentController();
+  if (controller) {
+    int32_t modifiers = WidgetModifiersToDOMModifiers(aEvent.modifiers);
+    CSSPoint geckoScreenPoint;
+    if (ConvertToGecko(aEvent.mPoint, &geckoScreenPoint)) {
+      SetState(WAITING_CONTENT_RESPONSE);
+      SetContentResponseTimer();
+      controller->HandleLongTap(geckoScreenPoint, modifiers, GetGuid());
+      return nsEventStatus_eConsumeNoDefault;
+    }
+  }
+  return nsEventStatus_eIgnore;
+}
+
+nsEventStatus AsyncPanZoomController::OnLongPressUp(const TapGestureInput& aEvent) {
+  APZC_LOG("%p got a long-tap-up in state %d\n", this, mState);
+  nsRefPtr<GeckoContentController> controller = GetGeckoContentController();
+  if (controller) {
+    int32_t modifiers = WidgetModifiersToDOMModifiers(aEvent.modifiers);
+    CSSPoint geckoScreenPoint;
+    if (ConvertToGecko(aEvent.mPoint, &geckoScreenPoint)) {
+      controller->HandleLongTapUp(geckoScreenPoint, modifiers, GetGuid());
+      return nsEventStatus_eConsumeNoDefault;
+    }
+  }
+  return nsEventStatus_eIgnore;
+}
+
+nsEventStatus AsyncPanZoomController::GenerateSingleTap(const ScreenIntPoint& aPoint, mozilla::Modifiers aModifiers) {
+  nsRefPtr<GeckoContentController> controller = GetGeckoContentController();
+  if (controller) {
+    CSSPoint geckoScreenPoint;
+    if (ConvertToGecko(aPoint, &geckoScreenPoint)) {
+      int32_t modifiers = WidgetModifiersToDOMModifiers(aModifiers);
+      // Because this may be being running as part of APZCTreeManager::ReceiveInputEvent,
+      // calling controller->HandleSingleTap directly might mean that content receives
+      // the single tap message before the corresponding touch-up. To avoid that we
+      // schedule the singletap message to run on the next spin of the event loop.
+      // See bug 965381 for the issue this was causing.
+      controller->PostDelayedTask(
+        NewRunnableMethod(controller.get(), &GeckoContentController::HandleSingleTap,
+                          geckoScreenPoint, modifiers, GetGuid()),
+        0);
+      mTouchBlockState.mSingleTapOccurred = true;
+      return nsEventStatus_eConsumeNoDefault;
+    }
+  }
+  return nsEventStatus_eIgnore;
+}
+
+void AsyncPanZoomController::OnTouchEndOrCancel() {
+  if (nsRefPtr<GeckoContentController> controller = GetGeckoContentController()) {
+    controller->NotifyAPZStateChange(
+        GetGuid(), APZStateChange::EndTouch, mTouchBlockState.mSingleTapOccurred);
+  }
+}
+
+nsEventStatus AsyncPanZoomController::OnSingleTapUp(const TapGestureInput& aEvent) {
+  APZC_LOG("%p got a single-tap-up in state %d\n", this, mState);
+  // If mZoomConstraints.mAllowDoubleTapZoom is true we wait for a call to OnSingleTapConfirmed before
+  // sending event to content
+  if (!(mZoomConstraints.mAllowDoubleTapZoom && TouchActionAllowDoubleTapZoom())) {
+    return GenerateSingleTap(aEvent.mPoint, aEvent.modifiers);
+  }
+  return nsEventStatus_eIgnore;
+}
+
+nsEventStatus AsyncPanZoomController::OnSingleTapConfirmed(const TapGestureInput& aEvent) {
+  APZC_LOG("%p got a single-tap-confirmed in state %d\n", this, mState);
+  return GenerateSingleTap(aEvent.mPoint, aEvent.modifiers);
+}
+
+nsEventStatus AsyncPanZoomController::OnDoubleTap(const TapGestureInput& aEvent) {
+  APZC_LOG("%p got a double-tap in state %d\n", this, mState);
+  nsRefPtr<GeckoContentController> controller = GetGeckoContentController();
+  if (controller) {
+    if (mZoomConstraints.mAllowDoubleTapZoom && TouchActionAllowDoubleTapZoom()) {
+      int32_t modifiers = WidgetModifiersToDOMModifiers(aEvent.modifiers);
+      CSSPoint geckoScreenPoint;
+      if (ConvertToGecko(aEvent.mPoint, &geckoScreenPoint)) {
+        controller->HandleDoubleTap(geckoScreenPoint, modifiers, GetGuid());
+      }
+    }
+    return nsEventStatus_eConsumeNoDefault;
+  }
+  return nsEventStatus_eIgnore;
+}
+
+nsEventStatus AsyncPanZoomController::OnCancelTap(const TapGestureInput& aEvent) {
+  APZC_LOG("%p got a cancel-tap in state %d\n", this, mState);
+  // XXX: Implement this.
+  return nsEventStatus_eIgnore;
+}
+
+float AsyncPanZoomController::PanDistance() {
+  ReentrantMonitorAutoEnter lock(mMonitor);
+  return NS_hypot(mX.PanDistance(), mY.PanDistance());
+}
+
+const ScreenPoint AsyncPanZoomController::GetVelocityVector() {
+  return ScreenPoint(mX.GetVelocity(), mY.GetVelocity());
+}
+
+void AsyncPanZoomController::HandlePanningWithTouchAction(double aAngle, TouchBehaviorFlags aBehavior) {
+  // Handling of cross sliding will need to be added in this method after touch-action released
+  // enabled by default.
+  if ((aBehavior & AllowedTouchBehavior::VERTICAL_PAN) && (aBehavior & AllowedTouchBehavior::HORIZONTAL_PAN)) {
+    if (mX.Scrollable() && mY.Scrollable()) {
+      if (IsCloseToHorizontal(aAngle, AXIS_LOCK_ANGLE)) {
+        mY.SetAxisLocked(true);
+        SetState(PANNING_LOCKED_X);
+      } else if (IsCloseToVertical(aAngle, AXIS_LOCK_ANGLE)) {
+        mX.SetAxisLocked(true);
+        SetState(PANNING_LOCKED_Y);
+      } else {
+        SetState(PANNING);
+      }
+    } else if (mX.Scrollable() || mY.Scrollable()) {
+      SetState(PANNING);
+    } else {
+      SetState(NOTHING);
+    }
+  } else if (aBehavior & AllowedTouchBehavior::HORIZONTAL_PAN) {
+    // Using bigger angle for panning to keep behavior consistent
+    // with IE.
+    if (IsCloseToHorizontal(aAngle, ALLOWED_DIRECT_PAN_ANGLE)) {
+      mY.SetAxisLocked(true);
+      SetState(PANNING_LOCKED_X);
+      mPanDirRestricted = true;
+    } else {
+      // Don't treat these touches as pan/zoom movements since 'touch-action' value
+      // requires it.
+      SetState(NOTHING);
+    }
+  } else if (aBehavior & AllowedTouchBehavior::VERTICAL_PAN) {
+    if (IsCloseToVertical(aAngle, ALLOWED_DIRECT_PAN_ANGLE)) {
+      mX.SetAxisLocked(true);
+      SetState(PANNING_LOCKED_Y);
+      mPanDirRestricted = true;
+    } else {
+      SetState(NOTHING);
+    }
+  } else {
+    SetState(NOTHING);
+  }
+}
+
+void AsyncPanZoomController::HandlePanning(double aAngle) {
+  if (!gfxPrefs::APZCrossSlideEnabled() && (!mX.Scrollable() || !mY.Scrollable())) {
+    SetState(PANNING);
+  } else if (IsCloseToHorizontal(aAngle, AXIS_LOCK_ANGLE)) {
+    mY.SetAxisLocked(true);
+    if (mX.Scrollable()) {
+      SetState(PANNING_LOCKED_X);
+    } else {
+      SetState(CROSS_SLIDING_X);
+      mX.SetAxisLocked(true);
+    }
+  } else if (IsCloseToVertical(aAngle, AXIS_LOCK_ANGLE)) {
+    mX.SetAxisLocked(true);
+    if (mY.Scrollable()) {
+      SetState(PANNING_LOCKED_Y);
+    } else {
+      SetState(CROSS_SLIDING_Y);
+      mY.SetAxisLocked(true);
+    }
+  } else {
+    SetState(PANNING);
+  }
+}
+
+nsEventStatus AsyncPanZoomController::StartPanning(const MultiTouchInput& aEvent) {
+  ReentrantMonitorAutoEnter lock(mMonitor);
+
+  ScreenIntPoint point = GetFirstTouchScreenPoint(aEvent);
+  float dx = mX.PanDistance(point.x);
+  float dy = mY.PanDistance(point.y);
+
+  // When the touch move breaks through the pan threshold, reposition the touch down origin
+  // so the page won't jump when we start panning.
+  mX.StartTouch(point.x);
+  mY.StartTouch(point.y);
+  mLastEventTime = aEvent.mTime;
+
+  double angle = atan2(dy, dx); // range [-pi, pi]
+  angle = fabs(angle); // range [0, pi]
+
+  if (mTouchActionPropertyEnabled) {
+    HandlePanningWithTouchAction(angle, GetTouchBehavior(0));
+  } else {
+    if (GetAxisLockMode() == FREE) {
+      SetState(PANNING);
+    } else {
+      HandlePanning(angle);
+    }
+  }
+
+  if (IsPanningState(mState)) {
+    if (nsRefPtr<GeckoContentController> controller = GetGeckoContentController()) {
+      controller->NotifyAPZStateChange(GetGuid(), APZStateChange::StartPanning);
+    }
+    return nsEventStatus_eConsumeNoDefault;
+  }
+  // Don't consume an event that didn't trigger a panning.
+  return nsEventStatus_eIgnore;
+}
+
+void AsyncPanZoomController::UpdateWithTouchAtDevicePoint(const MultiTouchInput& aEvent) {
+  ScreenIntPoint point = GetFirstTouchScreenPoint(aEvent);
+  TimeDuration timeDelta = TimeDuration().FromMilliseconds(aEvent.mTime - mLastEventTime);
+
+  // Probably a duplicate event, just throw it away.
+  if (timeDelta.ToMilliseconds() <= EPSILON) {
+    return;
+  }
+
+  mX.UpdateWithTouchAtDevicePoint(point.x, timeDelta);
+  mY.UpdateWithTouchAtDevicePoint(point.y, timeDelta);
+}
+
+void AsyncPanZoomController::AttemptScroll(const ScreenPoint& aStartPoint,
+                                           const ScreenPoint& aEndPoint,
+                                           uint32_t aOverscrollHandoffChainIndex) {
+
+  // "start - end" rather than "end - start" because e.g. moving your finger
+  // down (*positive* direction along y axis) causes the vertical scroll offset
+  // to *decrease* as the page follows your finger.
+  ScreenPoint displacement = aStartPoint - aEndPoint;
+
+  ScreenPoint overscroll;  // will be used outside monitor block
+  {
+    ReentrantMonitorAutoEnter lock(mMonitor);
+
+    CSSToScreenScale zoom = mFrameMetrics.GetZoom();
+
+    // Inversely scale the offset by the resolution (when you're zoomed further in,
+    // the same swipe should move you a shorter distance).
+    CSSPoint cssDisplacement = displacement / zoom;
+
+    CSSPoint cssOverscroll;
+    CSSPoint allowedDisplacement(mX.AdjustDisplacement(cssDisplacement.x,
+                                                       cssOverscroll.x),
+                                 mY.AdjustDisplacement(cssDisplacement.y,
+                                                       cssOverscroll.y));
+    overscroll = cssOverscroll * zoom;
+
+    if (!IsZero(allowedDisplacement)) {
+      ScrollBy(allowedDisplacement);
+      ScheduleComposite();
+
+      TimeDuration timePaintDelta = mPaintThrottler.TimeSinceLastRequest(GetFrameTime());
+      if (timePaintDelta.ToMilliseconds() > gfxPrefs::APZPanRepaintInterval()) {
+        RequestContentRepaint();
+      }
+      UpdateSharedCompositorFrameMetrics();
+    }
+  }
+
+  if (!IsZero(overscroll)) {
+    // "+ overscroll" rather than "- overscroll" because "overscroll" is what's
+    // left of "displacement", and "displacement" is "start - end".
+    CallDispatchScroll(aEndPoint + overscroll, aEndPoint, aOverscrollHandoffChainIndex + 1);
+  }
+}
+
+void AsyncPanZoomController::TakeOverFling(ScreenPoint aVelocity) {
+  // We may have a pre-existing velocity for whatever reason (for example,
+  // a previously handed off fling). We don't want to clobber that.
+  mX.SetVelocity(mX.GetVelocity() + aVelocity.x);
+  mY.SetVelocity(mY.GetVelocity() + aVelocity.y);
+  SetState(FLING);
+  StartAnimation(new FlingAnimation(*this));
+}
+
+void AsyncPanZoomController::CallDispatchScroll(const ScreenPoint& aStartPoint, const ScreenPoint& aEndPoint,
+                                                uint32_t aOverscrollHandoffChainIndex) {
+  // Make a local copy of the tree manager pointer and check if it's not
+  // null before calling DispatchScroll(). This is necessary because
+  // Destroy(), which nulls out mTreeManager, could be called concurrently.
+  APZCTreeManager* treeManagerLocal = mTreeManager;
+  if (treeManagerLocal) {
+    treeManagerLocal->DispatchScroll(this, aStartPoint, aEndPoint,
+                                     aOverscrollHandoffChainIndex);
+  }
+}
+
+void AsyncPanZoomController::TrackTouch(const MultiTouchInput& aEvent) {
+  ScreenIntPoint prevTouchPoint(mX.GetPos(), mY.GetPos());
+  ScreenIntPoint touchPoint = GetFirstTouchScreenPoint(aEvent);
+  TimeDuration timeDelta = TimeDuration().FromMilliseconds(aEvent.mTime - mLastEventTime);
+
+  // Probably a duplicate event, just throw it away.
+  if (timeDelta.ToMilliseconds() <= EPSILON) {
+    return;
+  }
+
+  // If we're axis-locked, check if the user is trying to break the lock
+  if (GetAxisLockMode() == STICKY && !mPanDirRestricted) {
+    ScreenIntPoint point = GetFirstTouchScreenPoint(aEvent);
+    float dx = mX.PanDistance(point.x);
+    float dy = mY.PanDistance(point.y);
+
+    double angle = atan2(dy, dx); // range [-pi, pi]
+    angle = fabs(angle); // range [0, pi]
+
+    float breakThreshold = AXIS_BREAKOUT_THRESHOLD * APZCTreeManager::GetDPI();
+
+    if (fabs(dx) > breakThreshold || fabs(dy) > breakThreshold) {
+      if (mState == PANNING_LOCKED_X || mState == CROSS_SLIDING_X) {
+        if (!IsCloseToHorizontal(angle, AXIS_BREAKOUT_ANGLE)) {
+          mY.SetAxisLocked(false);
+          SetState(PANNING);
+        }
+      } else if (mState == PANNING_LOCKED_Y || mState == CROSS_SLIDING_Y) {
+        if (!IsCloseToVertical(angle, AXIS_BREAKOUT_ANGLE)) {
+          mX.SetAxisLocked(false);
+          SetState(PANNING);
+        }
+      }
+    }
+  }
+
+  UpdateWithTouchAtDevicePoint(aEvent);
+
+  CallDispatchScroll(prevTouchPoint, touchPoint, 0);
+}
+
+ScreenIntPoint& AsyncPanZoomController::GetFirstTouchScreenPoint(const MultiTouchInput& aEvent) {
+  return ((SingleTouchData&)aEvent.mTouches[0]).mScreenPoint;
+}
+
+bool FlingAnimation::Sample(FrameMetrics& aFrameMetrics,
+                            const TimeDuration& aDelta) {
+
+  // If the fling is handed off to our APZC from a child, on the first call to
+  // Sample() aDelta might be negative because it's computed as the sample time
+  // from SampleContentTransformForFrame() minus our APZC's mLastSampleTime
+  // which is the time the child handed off the fling from its call to
+  // SampleContentTransformForFrame() with the same sample time. If we allow
+  // the negative aDelta to be processed, it will yield a displacement in the
+  // direction opposite to the fling, which can cause us to overscroll and
+  // hand off the fling to _our_ parent, which effectively kills the fling.
+  if (aDelta.ToMilliseconds() <= 0) {
+    return true;
+  }
+
+  bool shouldContinueFlingX = mApzc.mX.FlingApplyFrictionOrCancel(aDelta),
+       shouldContinueFlingY = mApzc.mY.FlingApplyFrictionOrCancel(aDelta);
+  // If we shouldn't continue the fling, let's just stop and repaint.
+  if (!shouldContinueFlingX && !shouldContinueFlingY) {
+    return false;
+  }
+
+  // AdjustDisplacement() zeroes out the Axis velocity if we're in overscroll.
+  // Since we need to hand off the velocity to the tree manager in such a case,
+  // we save it here. Would be ScreenVector instead of ScreenPoint if we had
+  // vector classes.
+  ScreenPoint velocity(mApzc.mX.GetVelocity(), mApzc.mY.GetVelocity());
+
+  ScreenPoint offset = velocity * aDelta.ToMilliseconds();
+
+  // Inversely scale the offset by the resolution (when you're zoomed further in,
+  // the same swipe should move you a shorter distance).
+  CSSPoint cssOffset = offset / aFrameMetrics.GetZoom();
+  CSSPoint overscroll;
+  aFrameMetrics.ScrollBy(CSSPoint(
+    mApzc.mX.AdjustDisplacement(cssOffset.x, overscroll.x),
+    mApzc.mY.AdjustDisplacement(cssOffset.y, overscroll.y)
+  ));
+
+  // If the fling has caused us to reach the end of our scroll range, hand
+  // off the fling to the next APZC in the overscroll handoff chain.
+  if (!IsZero(overscroll)) {
+    // We may have reached the end of the scroll range along one axis but
+    // not the other. In such a case we only want to hand off the relevant
+    // component of the fling.
+    if (FuzzyEqualsMultiplicative(overscroll.x, 0.0f)) {
+      velocity.x = 0;
+    } else if (FuzzyEqualsMultiplicative(overscroll.y, 0.0f)) {
+      velocity.y = 0;
+    }
+
+    // To hand off the fling, we call APZCTreeManager::HandleFlingOverscroll()
+    // which starts a new fling in the next APZC in the handoff chain with
+    // the same velocity. For simplicity, the actual overscroll of the current
+    // sample is discarded rather than being handed off. The compositor should
+    // sample animations sufficiently frequently that this is not noticeable.
+
+    // Make a local copy of the tree manager pointer and check if it's not
+    // null before calling HandleFlingOverscroll(). This is necessary because
+    // Destroy(), which nulls out mTreeManager, could be called concurrently.
+    APZCTreeManager* treeManagerLocal = mApzc.mTreeManager;
+    if (treeManagerLocal) {
+      // APZC is holding mMonitor, so directly calling HandleFlingOverscroll()
+      // (which acquires the tree lock) would violate the lock ordering. Instead
+      // we schedule HandleFlingOverscroll() to be called after mMonitor is
+      // released.
+      mDeferredTasks.append(NewRunnableMethod(treeManagerLocal,
+                                              &APZCTreeManager::HandOffFling,
+                                              &mApzc,
+                                              velocity));
+    }
+  }
+
+  return true;
+}
+
+void AsyncPanZoomController::StartAnimation(AsyncPanZoomAnimation* aAnimation)
+{
+  ReentrantMonitorAutoEnter lock(mMonitor);
+  mAnimation = aAnimation;
+  mLastSampleTime = GetFrameTime();
+  ScheduleComposite();
+}
+
+void AsyncPanZoomController::CancelAnimation() {
+  ReentrantMonitorAutoEnter lock(mMonitor);
+  SetState(NOTHING);
+  mAnimation = nullptr;
+}
+
+void AsyncPanZoomController::SetCompositorParent(CompositorParent* aCompositorParent) {
+  mCompositorParent = aCompositorParent;
+}
+
+void AsyncPanZoomController::SetCrossProcessCompositorParent(PCompositorParent* aCrossProcessCompositorParent) {
+  mCrossProcessCompositorParent = aCrossProcessCompositorParent;
+}
+
+void AsyncPanZoomController::ScrollBy(const CSSPoint& aOffset) {
+  mFrameMetrics.ScrollBy(aOffset);
+}
+
+void AsyncPanZoomController::ScaleWithFocus(float aScale,
+                                            const CSSPoint& aFocus) {
+  mFrameMetrics.ZoomBy(aScale);
+  // We want to adjust the scroll offset such that the CSS point represented by aFocus remains
+  // at the same position on the screen before and after the change in zoom. The below code
+  // accomplishes this; see https://bugzilla.mozilla.org/show_bug.cgi?id=923431#c6 for an
+  // in-depth explanation of how.
+  mFrameMetrics.SetScrollOffset((mFrameMetrics.GetScrollOffset() + aFocus) - (aFocus / aScale));
+}
+
+/**
+ * Enlarges the displayport along both axes based on the velocity.
+ */
+static CSSSize
+CalculateDisplayPortSize(const CSSSize& aCompositionSize,
+                         const CSSPoint& aVelocity)
+{
+  float xMultiplier = fabsf(aVelocity.x) < gfxPrefs::APZMinSkateSpeed()
+                        ? gfxPrefs::APZXStationarySizeMultiplier()
+                        : gfxPrefs::APZXSkateSizeMultiplier();
+  float yMultiplier = fabsf(aVelocity.y) < gfxPrefs::APZMinSkateSpeed()
+                        ? gfxPrefs::APZYStationarySizeMultiplier()
+                        : gfxPrefs::APZYSkateSizeMultiplier();
+  return CSSSize(aCompositionSize.width * xMultiplier,
+                 aCompositionSize.height * yMultiplier);
+}
+
+/**
+ * Attempts to redistribute any area in the displayport that would get clipped
+ * by the scrollable rect, or be inaccessible due to disabled scrolling, to the
+ * other axis, while maintaining total displayport area.
+ */
+static void
+RedistributeDisplayPortExcess(CSSSize& aDisplayPortSize,
+                              const CSSRect& aScrollableRect)
+{
+  float xSlack = std::max(0.0f, aDisplayPortSize.width - aScrollableRect.width);
+  float ySlack = std::max(0.0f, aDisplayPortSize.height - aScrollableRect.height);
+
+  if (ySlack > 0) {
+    // Reassign wasted y-axis displayport to the x-axis
+    aDisplayPortSize.height -= ySlack;
+    float xExtra = ySlack * aDisplayPortSize.width / aDisplayPortSize.height;
+    aDisplayPortSize.width += xExtra;
+  } else if (xSlack > 0) {
+    // Reassign wasted x-axis displayport to the y-axis
+    aDisplayPortSize.width -= xSlack;
+    float yExtra = xSlack * aDisplayPortSize.height / aDisplayPortSize.width;
+    aDisplayPortSize.height += yExtra;
+  }
+}
+
+/* static */
+const LayerMargin AsyncPanZoomController::CalculatePendingDisplayPort(
+  const FrameMetrics& aFrameMetrics,
+  const ScreenPoint& aVelocity,
+  double aEstimatedPaintDuration)
+{
+  CSSSize compositionBounds = aFrameMetrics.CalculateCompositedSizeInCssPixels();
+  CSSSize compositionSize = aFrameMetrics.GetRootCompositionSize();
+  compositionSize =
+    CSSSize(std::min(compositionBounds.width, compositionSize.width),
+            std::min(compositionBounds.height, compositionSize.height));
+  CSSPoint velocity = aVelocity / aFrameMetrics.GetZoom();
+  CSSPoint scrollOffset = aFrameMetrics.GetScrollOffset();
+  CSSRect scrollableRect = aFrameMetrics.GetExpandedScrollableRect();
+
+  // Calculate the displayport size based on how fast we're moving along each axis.
+  CSSSize displayPortSize = CalculateDisplayPortSize(compositionSize, velocity);
+
+  if (gfxPrefs::APZEnlargeDisplayPortWhenClipped()) {
+    RedistributeDisplayPortExcess(displayPortSize, scrollableRect);
+  }
+
+  // Offset the displayport, depending on how fast we're moving and the
+  // estimated time it takes to paint, to try to minimise checkerboarding.
+  float estimatedPaintDurationMillis = (float)(aEstimatedPaintDuration * 1000.0);
+  float paintFactor = (gfxPrefs::APZUsePaintDuration() ? estimatedPaintDurationMillis : 50.0f);
+  CSSRect displayPort = CSSRect(scrollOffset + (velocity * paintFactor * gfxPrefs::APZVelocityBias()),
+                                displayPortSize);
+
+  // Re-center the displayport based on its expansion over the composition size.
+  displayPort.MoveBy((compositionSize.width - displayPort.width)/2.0f,
+                     (compositionSize.height - displayPort.height)/2.0f);
+
+  // Make sure the displayport remains within the scrollable rect.
+  displayPort = displayPort.ForceInside(scrollableRect) - scrollOffset;
+
+  APZC_LOG_FM(aFrameMetrics,
+    "Calculated displayport as (%f %f %f %f) from velocity (%f %f) paint time %f metrics",
+    displayPort.x, displayPort.y, displayPort.width, displayPort.height,
+    aVelocity.x, aVelocity.y, (float)estimatedPaintDurationMillis);
+
+  CSSMargin cssMargins;
+  cssMargins.left = -displayPort.x;
+  cssMargins.top = -displayPort.y;
+  cssMargins.right = displayPort.width - compositionSize.width - cssMargins.left;
+  cssMargins.bottom = displayPort.height - compositionSize.height - cssMargins.top;
+
+  LayerMargin layerMargins = cssMargins * aFrameMetrics.LayersPixelsPerCSSPixel();
+
+  return layerMargins;
+}
+
+void AsyncPanZoomController::ScheduleComposite() {
+  if (mCompositorParent) {
+    mCompositorParent->ScheduleRenderOnCompositorThread();
+  }
+}
+
+void AsyncPanZoomController::FlushRepaintForOverscrollHandoff() {
+  ReentrantMonitorAutoEnter lock(mMonitor);
+  RequestContentRepaint();
+  UpdateSharedCompositorFrameMetrics();
+}
+
+bool AsyncPanZoomController::IsPannable() const {
+  ReentrantMonitorAutoEnter lock(mMonitor);
+  return mX.HasRoomToPan() || mY.HasRoomToPan();
+}
+
+void AsyncPanZoomController::RequestContentRepaint() {
+  RequestContentRepaint(mFrameMetrics);
+}
+
+void AsyncPanZoomController::RequestContentRepaint(FrameMetrics& aFrameMetrics) {
+  aFrameMetrics.SetDisplayPortMargins(
+    CalculatePendingDisplayPort(aFrameMetrics,
+                                GetVelocityVector(),
+                                mPaintThrottler.AverageDuration().ToSeconds()));
+  aFrameMetrics.SetUseDisplayPortMargins();
+
+  // If we're trying to paint what we already think is painted, discard this
+  // request since it's a pointless paint.
+  LayerMargin marginDelta = mLastPaintRequestMetrics.GetDisplayPortMargins()
+                          - aFrameMetrics.GetDisplayPortMargins();
+  if (fabsf(marginDelta.left) < EPSILON &&
+      fabsf(marginDelta.top) < EPSILON &&
+      fabsf(marginDelta.right) < EPSILON &&
+      fabsf(marginDelta.bottom) < EPSILON &&
+      fabsf(mLastPaintRequestMetrics.GetScrollOffset().x -
+            aFrameMetrics.GetScrollOffset().x) < EPSILON &&
+      fabsf(mLastPaintRequestMetrics.GetScrollOffset().y -
+            aFrameMetrics.GetScrollOffset().y) < EPSILON &&
+      aFrameMetrics.GetZoom() == mLastPaintRequestMetrics.GetZoom() &&
+      fabsf(aFrameMetrics.mViewport.width - mLastPaintRequestMetrics.mViewport.width) < EPSILON &&
+      fabsf(aFrameMetrics.mViewport.height - mLastPaintRequestMetrics.mViewport.height) < EPSILON) {
+    return;
+  }
+
+  SendAsyncScrollEvent();
+  mPaintThrottler.PostTask(
+    FROM_HERE,
+    NewRunnableMethod(this,
+                      &AsyncPanZoomController::DispatchRepaintRequest,
+                      aFrameMetrics),
+    GetFrameTime());
+
+  aFrameMetrics.mPresShellId = mLastContentPaintMetrics.mPresShellId;
+  mLastPaintRequestMetrics = aFrameMetrics;
+}
+
+/*static*/ CSSRect
+GetDisplayPortRect(const FrameMetrics& aFrameMetrics)
+{
+  // This computation is based on what happens in CalculatePendingDisplayPort. If that
+  // changes then this might need to change too
+  CSSRect baseRect(aFrameMetrics.GetScrollOffset(),
+                   CSSSize(std::min(aFrameMetrics.CalculateCompositedSizeInCssPixels().width,
+                                    aFrameMetrics.GetRootCompositionSize().width),
+                           std::min(aFrameMetrics.CalculateCompositedSizeInCssPixels().height,
+                                    aFrameMetrics.GetRootCompositionSize().height)));
+  baseRect.Inflate(aFrameMetrics.GetDisplayPortMargins() / aFrameMetrics.LayersPixelsPerCSSPixel());
+  return baseRect;
+}
+
+void
+AsyncPanZoomController::DispatchRepaintRequest(const FrameMetrics& aFrameMetrics) {
+  nsRefPtr<GeckoContentController> controller = GetGeckoContentController();
+  if (controller) {
+    APZC_LOG_FM(aFrameMetrics, "%p requesting content repaint", this);
+    LogRendertraceRect(GetGuid(), "requested displayport", "yellow", GetDisplayPortRect(aFrameMetrics));
+
+    controller->RequestContentRepaint(aFrameMetrics);
+    mLastDispatchedPaintMetrics = aFrameMetrics;
+  }
+}
+
+void
+AsyncPanZoomController::FireAsyncScrollOnTimeout()
+{
+  if (mCurrentAsyncScrollOffset != mLastAsyncScrollOffset) {
+    ReentrantMonitorAutoEnter lock(mMonitor);
+    SendAsyncScrollEvent();
+  }
+  mAsyncScrollTimeoutTask = nullptr;
+}
+
+bool ZoomAnimation::Sample(FrameMetrics& aFrameMetrics,
+                           const TimeDuration& aDelta) {
+  mDuration += aDelta;
+  double animPosition = mDuration / ZOOM_TO_DURATION;
+
+  if (animPosition >= 1.0) {
+    aFrameMetrics.SetZoom(mEndZoom);
+    aFrameMetrics.SetScrollOffset(mEndOffset);
+    return false;
+  }
+
+  // Sample the zoom at the current time point.  The sampled zoom
+  // will affect the final computed resolution.
+  double sampledPosition = gComputedTimingFunction->GetValue(animPosition);
+
+  // We scale the scrollOffset linearly with sampledPosition, so the zoom
+  // needs to scale inversely to match.
+  aFrameMetrics.SetZoom(CSSToScreenScale(1 /
+    (sampledPosition / mEndZoom.scale +
+    (1 - sampledPosition) / mStartZoom.scale)));
+
+  aFrameMetrics.SetScrollOffset(CSSPoint::FromUnknownPoint(gfx::Point(
+    mEndOffset.x * sampledPosition + mStartOffset.x * (1 - sampledPosition),
+    mEndOffset.y * sampledPosition + mStartOffset.y * (1 - sampledPosition)
+  )));
+
+  return true;
+}
+
+bool AsyncPanZoomController::UpdateAnimation(const TimeStamp& aSampleTime)
+{
+  if (mAnimation) {
+    if (mAnimation->Sample(mFrameMetrics, aSampleTime - mLastSampleTime)) {
+      if (mPaintThrottler.TimeSinceLastRequest(aSampleTime) >
+          mAnimation->mRepaintInterval) {
+        RequestContentRepaint();
+      }
+    } else {
+      mAnimation = nullptr;
+      SetState(NOTHING);
+      SendAsyncScrollEvent();
+      RequestContentRepaint();
+    }
+    UpdateSharedCompositorFrameMetrics();
+    mLastSampleTime = aSampleTime;
+    return true;
+  }
+  return false;
+}
+
+bool AsyncPanZoomController::SampleContentTransformForFrame(const TimeStamp& aSampleTime,
+                                                            ViewTransform* aNewTransform,
+                                                            ScreenPoint& aScrollOffset) {
+  // The eventual return value of this function. The compositor needs to know
+  // whether or not to advance by a frame as soon as it can. For example, if a
+  // fling is happening, it has to keep compositing so that the animation is
+  // smooth. If an animation frame is requested, it is the compositor's
+  // responsibility to schedule a composite.
+  bool requestAnimationFrame = false;
+  Vector<Task*> deferredTasks;
+
+  {
+    ReentrantMonitorAutoEnter lock(mMonitor);
+
+    requestAnimationFrame = UpdateAnimation(aSampleTime);
+
+    aScrollOffset = mFrameMetrics.GetScrollOffset() * mFrameMetrics.GetZoom();
+    *aNewTransform = GetCurrentAsyncTransform();
+
+    LogRendertraceRect(GetGuid(), "viewport", "red",
+      CSSRect(mFrameMetrics.GetScrollOffset(),
+              ParentLayerSize(mFrameMetrics.mCompositionBounds.Size()) / mFrameMetrics.GetZoomToParent()));
+
+    mCurrentAsyncScrollOffset = mFrameMetrics.GetScrollOffset();
+
+    // Get any deferred tasks queued up by mAnimation's Sample() (called by
+    // UpdateAnimation()). This needs to be done here since mAnimation can
+    // be destroyed by another thread when we release the monitor, but
+    // the tasks need to be executed after we release the monitor since they
+    // are allowed to call APZCTreeManager methods which can grab the tree lock. 
+    if (mAnimation) {
+      deferredTasks = mAnimation->TakeDeferredTasks();
+    }
+  }
+
+  for (uint32_t i = 0; i < deferredTasks.length(); ++i) {
+    deferredTasks[i]->Run();
+    delete deferredTasks[i];
+  }
+
+  // Cancel the mAsyncScrollTimeoutTask because we will fire a
+  // mozbrowserasyncscroll event or renew the mAsyncScrollTimeoutTask again.
+  if (mAsyncScrollTimeoutTask) {
+    mAsyncScrollTimeoutTask->Cancel();
+    mAsyncScrollTimeoutTask = nullptr;
+  }
+  // Fire the mozbrowserasyncscroll event immediately if it's been
+  // sAsyncScrollThrottleTime ms since the last time we fired the event and the
+  // current scroll offset is different than the mLastAsyncScrollOffset we sent
+  // with the last event.
+  // Otherwise, start a timer to fire the event sAsyncScrollTimeout ms from now.
+  TimeDuration delta = aSampleTime - mLastAsyncScrollTime;
+  if (delta.ToMilliseconds() > gfxPrefs::APZAsyncScrollThrottleTime() &&
+      mCurrentAsyncScrollOffset != mLastAsyncScrollOffset) {
+    ReentrantMonitorAutoEnter lock(mMonitor);
+    mLastAsyncScrollTime = aSampleTime;
+    mLastAsyncScrollOffset = mCurrentAsyncScrollOffset;
+    SendAsyncScrollEvent();
+  }
+  else {
+    mAsyncScrollTimeoutTask =
+      NewRunnableMethod(this, &AsyncPanZoomController::FireAsyncScrollOnTimeout);
+    MessageLoop::current()->PostDelayedTask(FROM_HERE,
+                                            mAsyncScrollTimeoutTask,
+                                            gfxPrefs::APZAsyncScrollTimeout());
+  }
+
+  return requestAnimationFrame;
+}
+
+ViewTransform AsyncPanZoomController::GetCurrentAsyncTransform() {
+  ReentrantMonitorAutoEnter lock(mMonitor);
+
+  CSSPoint lastPaintScrollOffset;
+  if (mLastContentPaintMetrics.IsScrollable()) {
+    lastPaintScrollOffset = mLastContentPaintMetrics.GetScrollOffset();
+  }
+
+  CSSPoint currentScrollOffset = mFrameMetrics.GetScrollOffset() +
+    mTestAsyncScrollOffset;
+
+  // If checkerboarding has been disallowed, clamp the scroll position to stay
+  // within rendered content.
+  if (!gfxPrefs::APZAllowCheckerboarding() &&
+      !mLastContentPaintMetrics.mDisplayPort.IsEmpty()) {
+    CSSSize compositedSize = mLastContentPaintMetrics.CalculateCompositedSizeInCssPixels();
+    CSSPoint maxScrollOffset = lastPaintScrollOffset +
+      CSSPoint(mLastContentPaintMetrics.mDisplayPort.XMost() - compositedSize.width,
+               mLastContentPaintMetrics.mDisplayPort.YMost() - compositedSize.height);
+    CSSPoint minScrollOffset = lastPaintScrollOffset + mLastContentPaintMetrics.mDisplayPort.TopLeft();
+
+    if (minScrollOffset.x < maxScrollOffset.x) {
+      currentScrollOffset.x = clamped(currentScrollOffset.x, minScrollOffset.x, maxScrollOffset.x);
+    }
+    if (minScrollOffset.y < maxScrollOffset.y) {
+      currentScrollOffset.y = clamped(currentScrollOffset.y, minScrollOffset.y, maxScrollOffset.y);
+    }
+  }
+
+  LayerPoint translation = (currentScrollOffset - lastPaintScrollOffset)
+                         * mLastContentPaintMetrics.LayersPixelsPerCSSPixel();
+
+  return ViewTransform(-translation,
+                       mFrameMetrics.GetZoom()
+                     / mLastContentPaintMetrics.mDevPixelsPerCSSPixel
+                     / mFrameMetrics.GetParentResolution());
+}
+
+gfx3DMatrix AsyncPanZoomController::GetNontransientAsyncTransform() {
+  ReentrantMonitorAutoEnter lock(mMonitor);
+  return gfx3DMatrix::ScalingMatrix(mLastContentPaintMetrics.mResolution.scale,
+                                    mLastContentPaintMetrics.mResolution.scale,
+                                    1.0f);
+}
+
+gfx3DMatrix AsyncPanZoomController::GetTransformToLastDispatchedPaint() {
+  ReentrantMonitorAutoEnter lock(mMonitor);
+  LayerPoint scrollChange = (mLastContentPaintMetrics.GetScrollOffset() - mLastDispatchedPaintMetrics.GetScrollOffset())
+                          * mLastContentPaintMetrics.LayersPixelsPerCSSPixel();
+  float zoomChange = mLastContentPaintMetrics.GetZoom().scale / mLastDispatchedPaintMetrics.GetZoom().scale;
+  return gfx3DMatrix::Translation(scrollChange.x, scrollChange.y, 0) *
+         gfx3DMatrix::ScalingMatrix(zoomChange, zoomChange, 1);
+}
+
+void AsyncPanZoomController::NotifyLayersUpdated(const FrameMetrics& aLayerMetrics, bool aIsFirstPaint) {
+  ReentrantMonitorAutoEnter lock(mMonitor);
+
+  mLastContentPaintMetrics = aLayerMetrics;
+  UpdateTransformScale();
+
+  bool isDefault = mFrameMetrics.IsDefault();
+  mFrameMetrics.mMayHaveTouchListeners = aLayerMetrics.mMayHaveTouchListeners;
+  APZC_LOG_FM(aLayerMetrics, "%p got a NotifyLayersUpdated with aIsFirstPaint=%d", this, aIsFirstPaint);
+
+  LogRendertraceRect(GetGuid(), "page", "brown", aLayerMetrics.mScrollableRect);
+  LogRendertraceRect(GetGuid(), "painted displayport", "green",
+    aLayerMetrics.mDisplayPort + aLayerMetrics.GetScrollOffset());
+
+  mPaintThrottler.TaskComplete(GetFrameTime());
+  bool needContentRepaint = false;
+  if (aLayerMetrics.mCompositionBounds.width == mFrameMetrics.mCompositionBounds.width &&
+      aLayerMetrics.mCompositionBounds.height == mFrameMetrics.mCompositionBounds.height) {
+    // Remote content has sync'd up to the composition geometry
+    // change, so we can accept the viewport it's calculated.
+    if (mFrameMetrics.mViewport.width != aLayerMetrics.mViewport.width ||
+        mFrameMetrics.mViewport.height != aLayerMetrics.mViewport.height) {
+      needContentRepaint = true;
+    }
+    mFrameMetrics.mViewport = aLayerMetrics.mViewport;
+  }
+
+  // If the layers update was not triggered by our own repaint request, then
+  // we want to take the new scroll offset. Check the scroll generation as well
+  // to filter duplicate calls to NotifyLayersUpdated with the same scroll offset
+  // update message.
+  bool scrollOffsetUpdated = aLayerMetrics.GetScrollOffsetUpdated()
+        && (aLayerMetrics.GetScrollGeneration() != mFrameMetrics.GetScrollGeneration());
+
+  if (aIsFirstPaint || isDefault) {
+    // Initialize our internal state to something sane when the content
+    // that was just painted is something we knew nothing about previously
+    mPaintThrottler.ClearHistory();
+    mPaintThrottler.SetMaxDurations(gfxPrefs::APZNumPaintDurationSamples());
+
+    mX.CancelTouch();
+    mY.CancelTouch();
+    SetState(NOTHING);
+
+    mFrameMetrics = aLayerMetrics;
+    mLastDispatchedPaintMetrics = aLayerMetrics;
+    ShareCompositorFrameMetrics();
+  } else {
+    // If we're not taking the aLayerMetrics wholesale we still need to pull
+    // in some things into our local mFrameMetrics because these things are
+    // determined by Gecko and our copy in mFrameMetrics may be stale.
+
+    if (mFrameMetrics.mCompositionBounds.width == aLayerMetrics.mCompositionBounds.width &&
+        mFrameMetrics.mDevPixelsPerCSSPixel == aLayerMetrics.mDevPixelsPerCSSPixel) {
+      float parentResolutionChange = aLayerMetrics.GetParentResolution().scale
+                                   / mFrameMetrics.GetParentResolution().scale;
+      mFrameMetrics.ZoomBy(parentResolutionChange);
+    } else {
+      // Take the new zoom as either device scale or composition width or both
+      // got changed (e.g. due to orientation change).
+      mFrameMetrics.SetZoom(aLayerMetrics.GetZoom());
+      mFrameMetrics.mDevPixelsPerCSSPixel.scale = aLayerMetrics.mDevPixelsPerCSSPixel.scale;
+    }
+    mFrameMetrics.mScrollableRect = aLayerMetrics.mScrollableRect;
+    mFrameMetrics.mCompositionBounds = aLayerMetrics.mCompositionBounds;
+    mFrameMetrics.SetRootCompositionSize(aLayerMetrics.GetRootCompositionSize());
+    mFrameMetrics.mResolution = aLayerMetrics.mResolution;
+    mFrameMetrics.mCumulativeResolution = aLayerMetrics.mCumulativeResolution;
+    mFrameMetrics.mHasScrollgrab = aLayerMetrics.mHasScrollgrab;
+
+    if (scrollOffsetUpdated) {
+      APZC_LOG("%p updating scroll offset from (%f, %f) to (%f, %f)\n", this,
+        mFrameMetrics.GetScrollOffset().x, mFrameMetrics.GetScrollOffset().y,
+        aLayerMetrics.GetScrollOffset().x, aLayerMetrics.GetScrollOffset().y);
+
+      mFrameMetrics.CopyScrollInfoFrom(aLayerMetrics);
+
+      // Because of the scroll offset update, any inflight paint requests are
+      // going to be ignored by layout, and so mLastDispatchedPaintMetrics
+      // becomes incorrect for the purposes of calculating the LD transform. To
+      // correct this we need to update mLastDispatchedPaintMetrics to be the
+      // last thing we know was painted by Gecko.
+      mLastDispatchedPaintMetrics = aLayerMetrics;
+    }
+  }
+
+  if (scrollOffsetUpdated) {
+    // Once layout issues a scroll offset update, it becomes impervious to
+    // scroll offset updates from APZ until we acknowledge the update it sent.
+    // This prevents APZ updates from clobbering scroll updates from other
+    // more "legitimate" sources like content scripts.
+    nsRefPtr<GeckoContentController> controller = GetGeckoContentController();
+    if (controller) {
+      APZC_LOG("%p sending scroll update acknowledgement with gen %lu\n", this, aLayerMetrics.GetScrollGeneration());
+      controller->AcknowledgeScrollUpdate(aLayerMetrics.GetScrollId(),
+                                          aLayerMetrics.GetScrollGeneration());
+    }
+  }
+
+  if (needContentRepaint) {
+    RequestContentRepaint();
+  }
+  UpdateSharedCompositorFrameMetrics();
+}
+
+const FrameMetrics& AsyncPanZoomController::GetFrameMetrics() {
+  mMonitor.AssertCurrentThreadIn();
+  return mFrameMetrics;
+}
+
+void AsyncPanZoomController::ZoomToRect(CSSRect aRect) {
+  if (!aRect.IsFinite()) {
+    NS_WARNING("ZoomToRect got called with a non-finite rect; ignoring...\n");
+    return;
+  }
+
+  SetState(ANIMATING_ZOOM);
+
+  {
+    ReentrantMonitorAutoEnter lock(mMonitor);
+
+    ParentLayerIntRect compositionBounds = mFrameMetrics.mCompositionBounds;
+    CSSRect cssPageRect = mFrameMetrics.mScrollableRect;
+    CSSPoint scrollOffset = mFrameMetrics.GetScrollOffset();
+    CSSToParentLayerScale currentZoom = mFrameMetrics.GetZoomToParent();
+    CSSToParentLayerScale targetZoom;
+
+    // The minimum zoom to prevent over-zoom-out.
+    // If the zoom factor is lower than this (i.e. we are zoomed more into the page),
+    // then the CSS content rect, in layers pixels, will be smaller than the
+    // composition bounds. If this happens, we can't fill the target composited
+    // area with this frame.
+    CSSToParentLayerScale localMinZoom(std::max((mZoomConstraints.mMinZoom * mFrameMetrics.mTransformScale).scale,
+                                       std::max(compositionBounds.width / cssPageRect.width,
+                                                compositionBounds.height / cssPageRect.height)));
+    CSSToParentLayerScale localMaxZoom = mZoomConstraints.mMaxZoom * mFrameMetrics.mTransformScale;
+
+    if (!aRect.IsEmpty()) {
+      // Intersect the zoom-to-rect to the CSS rect to make sure it fits.
+      aRect = aRect.Intersect(cssPageRect);
+      targetZoom = CSSToParentLayerScale(std::min(compositionBounds.width / aRect.width,
+                                                  compositionBounds.height / aRect.height));
+    }
+    // 1. If the rect is empty, request received from browserElementScrolling.js
+    // 2. currentZoom is equal to mZoomConstraints.mMaxZoom and user still double-tapping it
+    // 3. currentZoom is equal to localMinZoom and user still double-tapping it
+    // Treat these three cases as a request to zoom out as much as possible.
+    if (aRect.IsEmpty() ||
+        (currentZoom == localMaxZoom && targetZoom >= localMaxZoom) ||
+        (currentZoom == localMinZoom && targetZoom <= localMinZoom)) {
+      CSSSize compositedSize = mFrameMetrics.CalculateCompositedSizeInCssPixels();
+      float y = scrollOffset.y;
+      float newHeight =
+        cssPageRect.width * (compositedSize.height / compositedSize.width);
+      float dh = compositedSize.height - newHeight;
+
+      aRect = CSSRect(0.0f,
+                      y + dh/2,
+                      cssPageRect.width,
+                      newHeight);
+      aRect = aRect.Intersect(cssPageRect);
+      targetZoom = CSSToParentLayerScale(std::min(compositionBounds.width / aRect.width,
+                                                  compositionBounds.height / aRect.height));
+    }
+
+    targetZoom.scale = clamped(targetZoom.scale, localMinZoom.scale, localMaxZoom.scale);
+    FrameMetrics endZoomToMetrics = mFrameMetrics;
+    endZoomToMetrics.SetZoom(targetZoom / mFrameMetrics.mTransformScale);
+
+    // Adjust the zoomToRect to a sensible position to prevent overscrolling.
+    CSSSize sizeAfterZoom = endZoomToMetrics.CalculateCompositedSizeInCssPixels();
+
+    // If either of these conditions are met, the page will be
+    // overscrolled after zoomed
+    if (aRect.y + sizeAfterZoom.height > cssPageRect.height) {
+      aRect.y = cssPageRect.height - sizeAfterZoom.height;
+      aRect.y = aRect.y > 0 ? aRect.y : 0;
+    }
+    if (aRect.x + sizeAfterZoom.width > cssPageRect.width) {
+      aRect.x = cssPageRect.width - sizeAfterZoom.width;
+      aRect.x = aRect.x > 0 ? aRect.x : 0;
+    }
+
+    endZoomToMetrics.SetScrollOffset(aRect.TopLeft());
+    endZoomToMetrics.SetDisplayPortMargins(
+      CalculatePendingDisplayPort(endZoomToMetrics,
+                                  ScreenPoint(0,0),
+                                  0));
+    endZoomToMetrics.SetUseDisplayPortMargins();
+
+    StartAnimation(new ZoomAnimation(
+        mFrameMetrics.GetScrollOffset(),
+        mFrameMetrics.GetZoom(),
+        endZoomToMetrics.GetScrollOffset(),
+        endZoomToMetrics.GetZoom()));
+
+    // Schedule a repaint now, so the new displayport will be painted before the
+    // animation finishes.
+    RequestContentRepaint(endZoomToMetrics);
+  }
+}
+
+void AsyncPanZoomController::ContentReceivedTouch(bool aPreventDefault) {
+  mTouchBlockState.mPreventDefaultSet = true;
+  mTouchBlockState.mPreventDefault = aPreventDefault;
+  CheckContentResponse();
+}
+
+void AsyncPanZoomController::CheckContentResponse() {
+  bool canProceedToTouchState = true;
+
+  if (mFrameMetrics.mMayHaveTouchListeners) {
+    canProceedToTouchState &= mTouchBlockState.mPreventDefaultSet;
+  }
+
+  if (mTouchActionPropertyEnabled) {
+    canProceedToTouchState &= mTouchBlockState.mAllowedTouchBehaviorSet;
+  }
+
+  if (!canProceedToTouchState) {
+    return;
+  }
+
+  if (mContentResponseTimeoutTask) {
+    mContentResponseTimeoutTask->Cancel();
+    mContentResponseTimeoutTask = nullptr;
+  }
+
+  if (mState == WAITING_CONTENT_RESPONSE) {
+    if (!mTouchBlockState.mPreventDefault) {
+      SetState(NOTHING);
+    }
+
+    mHandlingTouchQueue = true;
+
+    while (!mTouchQueue.IsEmpty()) {
+      if (!mTouchBlockState.mPreventDefault) {
+        HandleInputEvent(mTouchQueue[0]);
+      }
+
+      if (mTouchQueue[0].mType == MultiTouchInput::MULTITOUCH_END ||
+          mTouchQueue[0].mType == MultiTouchInput::MULTITOUCH_CANCEL) {
+        mTouchQueue.RemoveElementAt(0);
+        break;
+      }
+
+      mTouchQueue.RemoveElementAt(0);
+    }
+
+    mHandlingTouchQueue = false;
+  }
+}
+
+bool AsyncPanZoomController::TouchActionAllowPinchZoom() {
+  if (!mTouchActionPropertyEnabled) {
+    return true;
+  }
+  // Pointer events specification implies all touch points to allow zoom
+  // to perform it.
+  for (size_t i = 0; i < mTouchBlockState.mAllowedTouchBehaviors.Length(); i++) {
+    if (!(mTouchBlockState.mAllowedTouchBehaviors[i] & AllowedTouchBehavior::PINCH_ZOOM)) {
+      return false;
+    }
+  }
+  return true;
+}
+
+bool AsyncPanZoomController::TouchActionAllowDoubleTapZoom() {
+  if (!mTouchActionPropertyEnabled) {
+    return true;
+  }
+  for (size_t i = 0; i < mTouchBlockState.mAllowedTouchBehaviors.Length(); i++) {
+    if (!(mTouchBlockState.mAllowedTouchBehaviors[i] & AllowedTouchBehavior::DOUBLE_TAP_ZOOM)) {
+      return false;
+    }
+  }
+  return true;
+}
+
+AsyncPanZoomController::TouchBehaviorFlags
+AsyncPanZoomController::GetTouchBehavior(uint32_t touchIndex) {
+  if (touchIndex < mTouchBlockState.mAllowedTouchBehaviors.Length()) {
+    return mTouchBlockState.mAllowedTouchBehaviors[touchIndex];
+  }
+  return DefaultTouchBehavior;
+}
+
+AsyncPanZoomController::TouchBehaviorFlags
+AsyncPanZoomController::GetAllowedTouchBehavior(ScreenIntPoint& aPoint) {
+  // Here we need to perform a hit testing over the touch-action regions attached to the
+  // layer associated with current apzc.
+  // Currently they are in progress, for more info see bug 928833.
+  return AllowedTouchBehavior::UNKNOWN;
+}
+
+void AsyncPanZoomController::SetAllowedTouchBehavior(const nsTArray<TouchBehaviorFlags>& aBehaviors) {
+  mTouchBlockState.mAllowedTouchBehaviors.Clear();
+  mTouchBlockState.mAllowedTouchBehaviors.AppendElements(aBehaviors);
+  mTouchBlockState.mAllowedTouchBehaviorSet = true;
+  CheckContentResponse();
+}
+
+void AsyncPanZoomController::SetState(PanZoomState aNewState) {
+
+  PanZoomState oldState;
+
+  // Intentional scoping for mutex
+  {
+    ReentrantMonitorAutoEnter lock(mMonitor);
+    oldState = mState;
+    mState = aNewState;
+  }
+
+  if (nsRefPtr<GeckoContentController> controller = GetGeckoContentController()) {
+    if (!IsTransformingState(oldState) && IsTransformingState(aNewState)) {
+      controller->NotifyAPZStateChange(
+          GetGuid(), APZStateChange::TransformBegin);
+    } else if (IsTransformingState(oldState) && !IsTransformingState(aNewState)) {
+      controller->NotifyAPZStateChange(
+          GetGuid(), APZStateChange::TransformEnd);
+    }
+  }
+}
+
+bool AsyncPanZoomController::IsTransformingState(PanZoomState aState) {
+  return !(aState == NOTHING || aState == TOUCHING || aState == WAITING_CONTENT_RESPONSE);
+}
+
+bool AsyncPanZoomController::IsPanningState(PanZoomState aState) {
+  return (aState == PANNING || aState == PANNING_LOCKED_X || aState == PANNING_LOCKED_Y);
+}
+
+void AsyncPanZoomController::SetContentResponseTimer() {
+  if (!mContentResponseTimeoutTask) {
+    mContentResponseTimeoutTask =
+      NewRunnableMethod(this, &AsyncPanZoomController::TimeoutContentResponse);
+
+    PostDelayedTask(mContentResponseTimeoutTask, gfxPrefs::APZContentResponseTimeout());
+  }
+}
+
+void AsyncPanZoomController::TimeoutContentResponse() {
+  mContentResponseTimeoutTask = nullptr;
+  ContentReceivedTouch(false);
+}
+
+void AsyncPanZoomController::UpdateZoomConstraints(const ZoomConstraints& aConstraints) {
+  APZC_LOG("%p updating zoom constraints to %d %d %f %f\n", this, aConstraints.mAllowZoom,
+    aConstraints.mAllowDoubleTapZoom, aConstraints.mMinZoom.scale, aConstraints.mMaxZoom.scale);
+  if (IsNaN(aConstraints.mMinZoom.scale) || IsNaN(aConstraints.mMaxZoom.scale)) {
+    NS_WARNING("APZC received zoom constraints with NaN values; dropping...\n");
+    return;
+  }
+  // inf float values and other bad cases should be sanitized by the code below.
+  mZoomConstraints.mAllowZoom = aConstraints.mAllowZoom;
+  mZoomConstraints.mAllowDoubleTapZoom = aConstraints.mAllowDoubleTapZoom;
+  mZoomConstraints.mMinZoom = (MIN_ZOOM > aConstraints.mMinZoom ? MIN_ZOOM : aConstraints.mMinZoom);
+  mZoomConstraints.mMaxZoom = (MAX_ZOOM > aConstraints.mMaxZoom ? aConstraints.mMaxZoom : MAX_ZOOM);
+  if (mZoomConstraints.mMaxZoom < mZoomConstraints.mMinZoom) {
+    mZoomConstraints.mMaxZoom = mZoomConstraints.mMinZoom;
+  }
+}
+
+ZoomConstraints
+AsyncPanZoomController::GetZoomConstraints() const
+{
+  return mZoomConstraints;
+}
+
+
+void AsyncPanZoomController::PostDelayedTask(Task* aTask, int aDelayMs) {
+  nsRefPtr<GeckoContentController> controller = GetGeckoContentController();
+  if (controller) {
+    controller->PostDelayedTask(aTask, aDelayMs);
+  }
+}
+
+void AsyncPanZoomController::SendAsyncScrollEvent() {
+  nsRefPtr<GeckoContentController> controller = GetGeckoContentController();
+  if (!controller) {
+    return;
+  }
+
+  bool isRoot;
+  CSSRect contentRect;
+  CSSSize scrollableSize;
+  {
+    ReentrantMonitorAutoEnter lock(mMonitor);
+
+    isRoot = mFrameMetrics.mIsRoot;
+    scrollableSize = mFrameMetrics.mScrollableRect.Size();
+    contentRect = mFrameMetrics.CalculateCompositedRectInCssPixels();
+    contentRect.MoveTo(mCurrentAsyncScrollOffset);
+  }
+
+  controller->SendAsyncScrollDOMEvent(isRoot, contentRect, scrollableSize);
+}
+
+bool AsyncPanZoomController::Matches(const ScrollableLayerGuid& aGuid)
+{
+  return aGuid == GetGuid();
+}
+
+void AsyncPanZoomController::GetGuid(ScrollableLayerGuid* aGuidOut)
+{
+  if (aGuidOut) {
+    *aGuidOut = GetGuid();
+  }
+}
+
+ScrollableLayerGuid AsyncPanZoomController::GetGuid()
+{
+  return ScrollableLayerGuid(mLayersId, mFrameMetrics);
+}
+
+void AsyncPanZoomController::UpdateSharedCompositorFrameMetrics()
+{
+  mMonitor.AssertCurrentThreadIn();
+
+  FrameMetrics* frame = mSharedFrameMetricsBuffer ?
+      static_cast<FrameMetrics*>(mSharedFrameMetricsBuffer->memory()) : nullptr;
+
+  if (frame && mSharedLock && gfxPrefs::UseProgressiveTilePainting()) {
+    mSharedLock->Lock();
+    *frame = mFrameMetrics;
+    mSharedLock->Unlock();
+  }
+}
+
+void AsyncPanZoomController::ShareCompositorFrameMetrics() {
+
+  PCompositorParent* compositor =
+    (mCrossProcessCompositorParent ? mCrossProcessCompositorParent : mCompositorParent.get());
+
+  // Only create the shared memory buffer if it hasn't already been created,
+  // we are using progressive tile painting, and we have a
+  // compositor to pass the shared memory back to the content process/thread.
+  if (!mSharedFrameMetricsBuffer && compositor && gfxPrefs::UseProgressiveTilePainting()) {
+
+    // Create shared memory and initialize it with the current FrameMetrics value
+    mSharedFrameMetricsBuffer = new ipc::SharedMemoryBasic;
+    FrameMetrics* frame = nullptr;
+    mSharedFrameMetricsBuffer->Create(sizeof(FrameMetrics));
+    mSharedFrameMetricsBuffer->Map(sizeof(FrameMetrics));
+    frame = static_cast<FrameMetrics*>(mSharedFrameMetricsBuffer->memory());
+
+    if (frame) {
+
+      { // scope the monitor, only needed to copy the FrameMetrics.
+        ReentrantMonitorAutoEnter lock(mMonitor);
+        *frame = mFrameMetrics;
+      }
+
+      // Get the process id of the content process
+      base::ProcessHandle processHandle = compositor->OtherProcess();
+      ipc::SharedMemoryBasic::Handle mem = ipc::SharedMemoryBasic::NULLHandle();
+
+      // Get the shared memory handle to share with the content process
+      mSharedFrameMetricsBuffer->ShareToProcess(processHandle, &mem);
+
+      // Get the cross process mutex handle to share with the content process
+      mSharedLock = new CrossProcessMutex("AsyncPanZoomControlLock");
+      CrossProcessMutexHandle handle = mSharedLock->ShareToProcess(processHandle);
+
+      // Send the shared memory handle and cross process handle to the content
+      // process by an asynchronous ipc call. Include the APZC unique ID
+      // so the content process know which APZC sent this shared FrameMetrics.
+      if (!compositor->SendSharedCompositorFrameMetrics(mem, handle, mAPZCId)) {
+        APZC_LOG("%p failed to share FrameMetrics with content process.", this);
+      }
+    }
+  }
+}
+
+ParentLayerPoint AsyncPanZoomController::ToParentLayerCoords(const ScreenPoint& aPoint)
+{
+  return TransformTo<ParentLayerPixel>(GetNontransientAsyncTransform() * GetCSSTransform(), aPoint);
+}
+
+void AsyncPanZoomController::UpdateTransformScale()
+{
+  gfx3DMatrix nontransientTransforms = GetNontransientAsyncTransform() * GetCSSTransform();
+  if (!FuzzyEqualsMultiplicative(nontransientTransforms.GetXScale(), nontransientTransforms.GetYScale())) {
+    NS_WARNING("The x- and y-scales of the nontransient transforms should be equal");
+  }
+  mFrameMetrics.mTransformScale.scale = nontransientTransforms.GetXScale();
+}
+
+}
+}