diff -r 000000000000 -r 6474c204b198 dom/browser-element/BrowserElementPanning.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/browser-element/BrowserElementPanning.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,860 @@
+/* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 sw=2 sts=2 et: */
+
+/* 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/. */
+
+"use strict";
+dump("############################### browserElementPanning.js loaded\n");
+
+let { classes: Cc, interfaces: Ci, results: Cr, utils: Cu }  = Components;
+Cu.import("resource://gre/modules/Services.jsm");
+Cu.import("resource://gre/modules/Geometry.jsm");
+
+var global = this;
+
+const kObservedEvents = [
+  "BEC:ShownModalPrompt",
+  "Activity:Success",
+  "Activity:Error"
+];
+
+const ContentPanning = {
+  // Are we listening to touch or mouse events?
+  watchedEventsType: '',
+
+  // Are mouse events being delivered to this content along with touch
+  // events, in violation of spec?
+  hybridEvents: false,
+
+  init: function cp_init() {
+    // If APZ is enabled, we do active element handling in C++
+    // (see widget/xpwidgets/ActiveElementManager.h), and panning
+    // itself in APZ, so we don't need to handle any touch events here.
+    if (docShell.asyncPanZoomEnabled === false) {
+      this._setupListenersForPanning();
+    }
+
+    addEventListener("unload",
+		     this._unloadHandler.bind(this),
+		     /* useCapture = */ false,
+		     /* wantsUntrusted = */ false);
+
+    addMessageListener("Viewport:Change", this._recvViewportChange.bind(this));
+    addMessageListener("Gesture:DoubleTap", this._recvDoubleTap.bind(this));
+    addEventListener("visibilitychange", this._handleVisibilityChange.bind(this));
+    kObservedEvents.forEach((topic) => {
+      Services.obs.addObserver(this, topic, false);
+    });
+  },
+
+  _setupListenersForPanning: function cp_setupListenersForPanning() {
+    var events;
+    try {
+      content.document.createEvent('TouchEvent');
+      events = ['touchstart', 'touchend', 'touchmove'];
+      this.watchedEventsType = 'touch';
+#ifdef MOZ_WIDGET_GONK
+      // The gonk widget backend does not deliver mouse events per
+      // spec.  Third-party content isn't exposed to this behavior,
+      // but that behavior creates some extra work for us here.
+      let appInfo = Cc["@mozilla.org/xre/app-info;1"];
+      let isParentProcess =
+        !appInfo || appInfo.getService(Ci.nsIXULRuntime)
+                           .processType == Ci.nsIXULRuntime.PROCESS_TYPE_DEFAULT;
+      this.hybridEvents = isParentProcess;
+#endif
+    } catch(e) {
+      // Touch events aren't supported, so fall back on mouse.
+      events = ['mousedown', 'mouseup', 'mousemove'];
+      this.watchedEventsType = 'mouse';
+    }
+
+    let els = Cc["@mozilla.org/eventlistenerservice;1"]
+                .getService(Ci.nsIEventListenerService);
+
+    events.forEach(function(type) {
+      // Using the system group for mouse/touch events to avoid
+      // missing events if .stopPropagation() has been called.
+      els.addSystemEventListener(global, type,
+                                 this.handleEvent.bind(this),
+                                 /* useCapture = */ false);
+    }.bind(this));
+  },
+
+  handleEvent: function cp_handleEvent(evt) {
+    // Ignore events targeting a <iframe mozbrowser> since those will be
+    // handle by the BrowserElementPanning.js instance of it.
+    if (evt.target instanceof Ci.nsIMozBrowserFrame) {
+      return;
+    }
+
+    if (evt.defaultPrevented || evt.multipleActionsPrevented) {
+      // clean up panning state even if touchend/mouseup has been preventDefault.
+      if(evt.type === 'touchend' || evt.type === 'mouseup') {
+        if (this.dragging &&
+            (this.watchedEventsType === 'mouse' ||
+             this.findPrimaryPointer(evt.changedTouches))) {
+          this._finishPanning();
+        }
+      }
+      return;
+    }
+
+    switch (evt.type) {
+      case 'mousedown':
+      case 'touchstart':
+        this.onTouchStart(evt);
+        break;
+      case 'mousemove':
+      case 'touchmove':
+        this.onTouchMove(evt);
+        break;
+      case 'mouseup':
+      case 'touchend':
+        this.onTouchEnd(evt);
+        break;
+      case 'click':
+        evt.stopPropagation();
+        evt.preventDefault();
+
+        let target = evt.target;
+        let view = target.ownerDocument ? target.ownerDocument.defaultView
+                                        : target;
+        view.removeEventListener('click', this, true, true);
+        break;
+    }
+  },
+
+  observe: function cp_observe(subject, topic, data) {
+    this._resetHover();
+  },
+
+  position: new Point(0 , 0),
+
+  findPrimaryPointer: function cp_findPrimaryPointer(touches) {
+    if (!('primaryPointerId' in this))
+      return null;
+
+    for (let i = 0; i < touches.length; i++) {
+      if (touches[i].identifier === this.primaryPointerId) {
+        return touches[i];
+      }
+    }
+    return null;
+  },
+
+  onTouchStart: function cp_onTouchStart(evt) {
+    let screenX, screenY;
+    if (this.watchedEventsType == 'touch') {
+      if ('primaryPointerId' in this || evt.touches.length >= 2) {
+        this._resetActive();
+        return;
+      }
+
+      let firstTouch = evt.changedTouches[0];
+      this.primaryPointerId = firstTouch.identifier;
+      this.pointerDownTarget = firstTouch.target;
+      screenX = firstTouch.screenX;
+      screenY = firstTouch.screenY;
+    } else {
+      this.pointerDownTarget = evt.target;
+      screenX = evt.screenX;
+      screenY = evt.screenY;
+    }
+    this.dragging = true;
+    this.panning = false;
+
+    let oldTarget = this.target;
+    [this.target, this.scrollCallback] = this.getPannable(this.pointerDownTarget);
+
+    // If we have a pointer down target, we may need to fill in for EventStateManager
+    // in setting the active state on the target element.  Set a timer to
+    // ensure the pointer-down target is active.  (If it's already
+    // active, the timer is a no-op.)
+    if (this.pointerDownTarget !== null) {
+      // If there's no possibility this is a drag/pan, activate now.
+      // Otherwise wait a little bit to see if the gesture isn't a
+      // tap.
+      if (this.target === null) {
+        this.notify(this._activationTimer);
+      } else {
+        this._activationTimer.initWithCallback(this,
+                                               this._activationDelayMs,
+                                               Ci.nsITimer.TYPE_ONE_SHOT);
+      }
+    }
+
+    // If there is a pan animation running (from a previous pan gesture) and
+    // the user touch back the screen, stop this animation immediatly and
+    // prevent the possible click action if the touch happens on the same
+    // target.
+    this.preventNextClick = false;
+    if (KineticPanning.active) {
+      KineticPanning.stop();
+
+      if (oldTarget && oldTarget == this.target)
+        this.preventNextClick = true;
+    }
+
+    this.position.set(screenX, screenY);
+    KineticPanning.reset();
+    KineticPanning.record(new Point(0, 0), evt.timeStamp);
+
+    // We prevent start events to avoid sending a focus event at the end of this
+    // touch series. See bug 889717.
+    if ((this.panning || this.preventNextClick)) {
+      evt.preventDefault();
+    }
+  },
+
+  onTouchEnd: function cp_onTouchEnd(evt) {
+    let touch = null;
+    if (!this.dragging ||
+        (this.watchedEventsType == 'touch' &&
+         !(touch = this.findPrimaryPointer(evt.changedTouches)))) {
+      return;
+    }
+
+    // !isPan() and evt.detail should always give the same answer here
+    // since they use the same heuristics, but use the native gecko
+    // computation when possible.
+    //
+    // NB: when we're using touch events, then !KineticPanning.isPan()
+    // => this.panning, so we'll never attempt to block the click
+    // event.  That's OK however, because we won't fire a synthetic
+    // click when we're using touch events and this touch series
+    // wasn't a "tap" gesture.
+    let click = (this.watchedEventsType == 'mouse') ?
+      evt.detail : !KineticPanning.isPan();
+    // Additionally, if we're seeing non-compliant hybrid events, a
+    // "real" click will be generated if we started and ended on the
+    // same element.
+    if (this.hybridEvents) {
+      let target =
+        content.document.elementFromPoint(touch.clientX, touch.clientY);
+      click |= (target === this.pointerDownTarget);
+    }
+
+    if (this.target && click && (this.panning || this.preventNextClick)) {
+      if (this.hybridEvents) {
+        let target = this.target;
+        let view = target.ownerDocument ? target.ownerDocument.defaultView
+                                        : target;
+        view.addEventListener('click', this, true, true);
+      } else {
+        // We prevent end events to avoid sending a focus event. See bug 889717.
+        evt.preventDefault();
+      }
+    } else if (this.target && click && !this.panning) {
+      this.notify(this._activationTimer);
+    }
+
+    this._finishPanning();
+
+    // Now that we're done, avoid entraining the thing we just panned.
+    this.pointerDownTarget = null;
+  },
+
+  onTouchMove: function cp_onTouchMove(evt) {
+    if (!this.dragging)
+      return;
+
+    let screenX, screenY;
+    if (this.watchedEventsType == 'touch') {
+      let primaryTouch = this.findPrimaryPointer(evt.changedTouches);
+      if (evt.touches.length > 1 || !primaryTouch)
+        return;
+      screenX = primaryTouch.screenX;
+      screenY = primaryTouch.screenY;
+    } else {
+      screenX = evt.screenX;
+      screenY = evt.screenY;
+    }
+
+    let current = this.position;
+    let delta = new Point(screenX - current.x, screenY - current.y);
+    current.set(screenX, screenY);
+
+    KineticPanning.record(delta, evt.timeStamp);
+
+    let isPan = KineticPanning.isPan();
+
+    // If we've detected a pan gesture, cancel the active state of the
+    // current target.
+    if (!this.panning && isPan) {
+      this._resetActive();
+    }
+
+    // There's no possibility of us panning anything.
+    if (!this.scrollCallback) {
+      return;
+    }
+
+    // Scroll manually.
+    this.scrollCallback(delta.scale(-1));
+
+    if (!this.panning && isPan) {
+      this.panning = true;
+      this._activationTimer.cancel();
+    }
+
+    if (this.panning) {
+      // Only do this when we're actually executing a pan gesture.
+      // Otherwise synthetic mouse events will be canceled.
+      evt.stopPropagation();
+      evt.preventDefault();
+    }
+  },
+
+  // nsITimerCallback
+  notify: function cp_notify(timer) {
+    this._setActive(this.pointerDownTarget);
+  },
+
+  onKineticBegin: function cp_onKineticBegin(evt) {
+  },
+
+  onKineticPan: function cp_onKineticPan(delta) {
+    return !this.scrollCallback(delta);
+  },
+
+  onKineticEnd: function cp_onKineticEnd() {
+    if (!this.dragging)
+      this.scrollCallback = null;
+  },
+
+  getPannable: function cp_getPannable(node) {
+    let pannableNode = this._findPannable(node);
+    if (pannableNode) {
+      return [pannableNode, this._generateCallback(pannableNode)];
+    }
+
+    return [null, null];
+  },
+
+  _findPannable: function cp_findPannable(node) {
+    if (!(node instanceof Ci.nsIDOMHTMLElement) || node.tagName == 'HTML') {
+      return null;
+    }
+
+    let nodeContent = node.ownerDocument.defaultView;
+    while (!(node instanceof Ci.nsIDOMHTMLBodyElement)) {
+      let style = nodeContent.getComputedStyle(node, null);
+
+      let overflow = [style.getPropertyValue('overflow'),
+                      style.getPropertyValue('overflow-x'),
+                      style.getPropertyValue('overflow-y')];
+
+      let rect = node.getBoundingClientRect();
+      let isAuto = (overflow.indexOf('auto') != -1 &&
+                   (rect.height < node.scrollHeight ||
+                    rect.width < node.scrollWidth));
+
+      let isScroll = (overflow.indexOf('scroll') != -1);
+
+      let isScrollableTextarea = (node.tagName == 'TEXTAREA' &&
+          (node.scrollHeight > node.clientHeight ||
+           node.scrollWidth > node.clientWidth ||
+           ('scrollLeftMax' in node && node.scrollLeftMax > 0) ||
+           ('scrollTopMax' in node && node.scrollTopMax > 0)));
+      if (isScroll || isAuto || isScrollableTextarea) {
+        return node;
+      }
+
+      node = node.parentNode;
+    }
+
+    if (nodeContent.scrollMaxX || nodeContent.scrollMaxY) {
+      return nodeContent;
+    }
+
+    if (nodeContent.frameElement) {
+      return this._findPannable(nodeContent.frameElement);
+    }
+
+    return null;
+  },
+
+  _generateCallback: function cp_generateCallback(root) {
+    let firstScroll = true;
+    let target;
+    let current;
+    let win, doc, htmlNode, bodyNode;
+
+    function doScroll(node, delta) {
+      if (node instanceof Ci.nsIDOMHTMLElement) {
+        return node.scrollByNoFlush(delta.x, delta.y);
+      } else if (node instanceof Ci.nsIDOMWindow) {
+        win = node;
+        doc = win.document;
+
+        // "overflow:hidden" on either the <html> or the <body> node should
+        // prevent the user from scrolling the root viewport.
+        if (doc instanceof Ci.nsIDOMHTMLDocument) {
+          htmlNode = doc.documentElement;
+          bodyNode = doc.body;
+          if (win.getComputedStyle(htmlNode, null).overflowX == "hidden" ||
+              win.getComputedStyle(bodyNode, null).overflowX == "hidden") {
+            delta.x = 0;
+          }
+          if (win.getComputedStyle(htmlNode, null).overflowY == "hidden" ||
+              win.getComputedStyle(bodyNode, null).overflowY == "hidden") {
+            delta.y = 0;
+          }
+        }
+        let oldX = node.scrollX;
+        let oldY = node.scrollY;
+        node.scrollBy(delta.x, delta.y);
+        return (node.scrollX != oldX || node.scrollY != oldY);
+      }
+      // If we get here, |node| isn't an HTML element and it's not a window,
+      // but findPannable apparently thought it was scrollable... What is it?
+      return false;
+    }
+
+    function targetParent(node) {
+      return node.parentNode || node.frameElement || null;
+    }
+
+    function scroll(delta) {
+      current = root;
+      firstScroll = true;
+      while (current) {
+        if (doScroll(current, delta)) {
+          firstScroll = false;
+          return true;
+        }
+
+        // TODO The current code looks for possible scrolling regions only if
+        // this is the first scroll action but this should be more dynamic.
+        if (!firstScroll) {
+          return false;
+        }
+
+        current = ContentPanning._findPannable(targetParent(current));
+      }
+
+      // There is nothing scrollable here.
+      return false;
+    }
+    return scroll;
+  },
+
+  get _domUtils() {
+    delete this._domUtils;
+    return this._domUtils = Cc['@mozilla.org/inspector/dom-utils;1']
+                              .getService(Ci.inIDOMUtils);
+  },
+
+  get _activationTimer() {
+    delete this._activationTimer;
+    return this._activationTimer = Cc["@mozilla.org/timer;1"]
+                                     .createInstance(Ci.nsITimer);
+  },
+
+  get _activationDelayMs() {
+    let delay = Services.prefs.getIntPref('ui.touch_activation.delay_ms');
+    delete this._activationDelayMs;
+    return this._activationDelayMs = delay;
+  },
+
+  _resetActive: function cp_resetActive() {
+    let elt = this.pointerDownTarget || this.target;
+    let root = elt.ownerDocument || elt.document;
+    this._setActive(root.documentElement);
+  },
+
+  _resetHover: function cp_resetHover() {
+    const kStateHover = 0x00000004;
+    try {
+      let element = content.document.createElement('foo');
+      this._domUtils.setContentState(element, kStateHover);
+    } catch(e) {}
+  },
+
+  _setActive: function cp_setActive(elt) {
+    const kStateActive = 0x00000001;
+    this._domUtils.setContentState(elt, kStateActive);
+  },
+
+  _recvViewportChange: function(data) {
+    let metrics = data.json;
+    this._viewport = new Rect(metrics.x, metrics.y,
+                              metrics.viewport.width,
+                              metrics.viewport.height);
+    this._cssCompositedRect = new Rect(metrics.x, metrics.y,
+                                       metrics.cssCompositedRect.width,
+                                       metrics.cssCompositedRect.height);
+    this._cssPageRect = new Rect(metrics.cssPageRect.x,
+                                 metrics.cssPageRect.y,
+                                 metrics.cssPageRect.width,
+                                 metrics.cssPageRect.height);
+  },
+
+  _recvDoubleTap: function(data) {
+    let data = data.json;
+
+    // We haven't received a metrics update yet; don't do anything.
+    if (this._viewport == null) {
+      return;
+    }
+
+    let win = content;
+
+    let element = ElementTouchHelper.anyElementFromPoint(win, data.x, data.y);
+    if (!element) {
+      this._zoomOut();
+      return;
+    }
+
+    while (element && !this._shouldZoomToElement(element))
+      element = element.parentNode;
+
+    if (!element) {
+      this._zoomOut();
+    } else {
+      const margin = 15;
+      let rect = ElementTouchHelper.getBoundingContentRect(element);
+
+      let cssPageRect = this._cssPageRect;
+      let viewport = this._viewport;
+      let bRect = new Rect(Math.max(cssPageRect.x, rect.x - margin),
+                           rect.y,
+                           rect.w + 2 * margin,
+                           rect.h);
+      // constrict the rect to the screen's right edge
+      bRect.width = Math.min(bRect.width, cssPageRect.right - bRect.x);
+
+      // if the rect is already taking up most of the visible area and is stretching the
+      // width of the page, then we want to zoom out instead.
+      if (this._isRectZoomedIn(bRect, this._cssCompositedRect)) {
+        this._zoomOut();
+        return;
+      }
+
+      rect.x = Math.round(bRect.x);
+      rect.y = Math.round(bRect.y);
+      rect.w = Math.round(bRect.width);
+      rect.h = Math.round(bRect.height);
+
+      // if the block we're zooming to is really tall, and the user double-tapped
+      // more than a screenful of height from the top of it, then adjust the y-coordinate
+      // so that we center the actual point the user double-tapped upon. this prevents
+      // flying to the top of a page when double-tapping to zoom in (bug 761721).
+      // the 1.2 multiplier is just a little fuzz to compensate for bRect including horizontal
+      // margins but not vertical ones.
+      let cssTapY = viewport.y + data.y;
+      if ((bRect.height > rect.h) && (cssTapY > rect.y + (rect.h * 1.2))) {
+        rect.y = cssTapY - (rect.h / 2);
+      }
+
+      Services.obs.notifyObservers(docShell, 'browser-zoom-to-rect', JSON.stringify(rect));
+    }
+  },
+
+  _handleVisibilityChange: function(evt) {
+    if (!evt.target.hidden)
+      return;
+
+    this._resetHover();
+  },
+
+  _shouldZoomToElement: function(aElement) {
+    let win = aElement.ownerDocument.defaultView;
+    if (win.getComputedStyle(aElement, null).display == "inline")
+      return false;
+    if (aElement instanceof Ci.nsIDOMHTMLLIElement)
+      return false;
+    if (aElement instanceof Ci.nsIDOMHTMLQuoteElement)
+      return false;
+    return true;
+  },
+
+  _zoomOut: function() {
+    let rect = new Rect(0, 0, 0, 0);
+    Services.obs.notifyObservers(docShell, 'browser-zoom-to-rect', JSON.stringify(rect));
+  },
+
+  _isRectZoomedIn: function(aRect, aViewport) {
+    // This function checks to see if the area of the rect visible in the
+    // viewport (i.e. the "overlapArea" variable below) is approximately 
+    // the max area of the rect we can show.
+    let vRect = new Rect(aViewport.x, aViewport.y, aViewport.width, aViewport.height);
+    let overlap = vRect.intersect(aRect);
+    let overlapArea = overlap.width * overlap.height;
+    let availHeight = Math.min(aRect.width * vRect.height / vRect.width, aRect.height);
+    let showing = overlapArea / (aRect.width * availHeight);
+    let ratioW = (aRect.width / vRect.width);
+    let ratioH = (aRect.height / vRect.height);
+
+    return (showing > 0.9 && (ratioW > 0.9 || ratioH > 0.9)); 
+  },
+
+  _finishPanning: function() {
+    this.dragging = false;
+    delete this.primaryPointerId;
+    this._activationTimer.cancel();
+
+    // If there is a scroll action, let's do a manual kinetic panning action.
+    if (this.panning) {
+      KineticPanning.start(this);
+    }
+  },
+
+  _unloadHandler: function() {
+    kObservedEvents.forEach((topic) => {
+      Services.obs.removeObserver(this, topic);
+    });
+  }
+};
+
+// Min/max velocity of kinetic panning. This is in pixels/millisecond.
+const kMinVelocity = 0.2;
+const kMaxVelocity = 6;
+
+// Constants that affect the "friction" of the scroll pane.
+const kExponentialC = 1000;
+const kPolynomialC = 100 / 1000000;
+
+// How often do we change the position of the scroll pane?
+// Too often and panning may jerk near the end.
+// Too little and panning will be choppy. In milliseconds.
+const kUpdateInterval = 16;
+
+// The numbers of momentums to use for calculating the velocity of the pan.
+// Those are taken from the end of the action
+const kSamples = 5;
+
+const KineticPanning = {
+  _position: new Point(0, 0),
+  _velocity: new Point(0, 0),
+  _acceleration: new Point(0, 0),
+
+  get active() {
+    return this.target !== null;
+  },
+
+  target: null,
+  start: function kp_start(target) {
+    this.target = target;
+
+    // Calculate the initial velocity of the movement based on user input
+    let momentums = this.momentums;
+    let flick = momentums[momentums.length - 1].time - momentums[0].time < 300;
+
+    let distance = new Point(0, 0);
+    momentums.forEach(function(momentum) {
+      distance.add(momentum.dx, momentum.dy);
+    });
+
+    function clampFromZero(x, min, max) {
+      if (x >= 0)
+        return Math.max(min, Math.min(max, x));
+      return Math.min(-min, Math.max(-max, x));
+    }
+
+    let elapsed = momentums[momentums.length - 1].time - momentums[0].time;
+    let velocityX = clampFromZero(distance.x / elapsed, 0, kMaxVelocity);
+    let velocityY = clampFromZero(distance.y / elapsed, 0, kMaxVelocity);
+
+    let velocity = this._velocity;
+    if (flick) {
+      // Very fast pan action that does not generate a click are very often pan
+      // action. If this is a small gesture then it will not move the view a lot
+      // and so it will be above the minimun threshold and not generate any
+      // kinetic panning. This does not look on a device since this is often
+      // a real gesture, so let's lower the velocity threshold for such moves.
+      velocity.set(velocityX, velocityY);
+    } else {
+      velocity.set(Math.abs(velocityX) < kMinVelocity ? 0 : velocityX,
+                   Math.abs(velocityY) < kMinVelocity ? 0 : velocityY);
+    }
+    this.momentums = [];
+
+    // Set acceleration vector to opposite signs of velocity
+    function sign(x) {
+      return x ? (x > 0 ? 1 : -1) : 0;
+    }
+
+    this._acceleration.set(velocity.clone().map(sign).scale(-kPolynomialC));
+
+    // Reset the position
+    this._position.set(0, 0);
+
+    this._startAnimation();
+
+    this.target.onKineticBegin();
+  },
+
+  stop: function kp_stop() {
+    this.reset();
+
+    if (!this.target)
+      return;
+
+    this.target.onKineticEnd();
+    this.target = null;
+  },
+
+  reset: function kp_reset() {
+    this.momentums = [];
+    this.distance.set(0, 0);
+  },
+
+  momentums: [],
+  record: function kp_record(delta, timestamp) {
+    this.momentums.push({ 'time': this._getTime(timestamp),
+                          'dx' : delta.x, 'dy' : delta.y });
+
+    // We only need to keep kSamples in this.momentums.
+    if (this.momentums.length > kSamples) {
+      this.momentums.shift();
+    }
+
+    this.distance.add(delta.x, delta.y);
+  },
+
+  _getTime: function kp_getTime(time) {
+    // Touch events generated by the platform or hand-made are defined in
+    // microseconds instead of milliseconds. Bug 77992 will fix this at the
+    // platform level.
+    if (time > Date.now()) {
+      return Math.floor(time / 1000);
+    } else {
+      return time;
+    }
+  },
+
+  get threshold() {
+    let dpi = content.QueryInterface(Ci.nsIInterfaceRequestor)
+                     .getInterface(Ci.nsIDOMWindowUtils)
+                     .displayDPI;
+
+    let threshold = Services.prefs.getIntPref('ui.dragThresholdX') / 240 * dpi;
+
+    delete this.threshold;
+    return this.threshold = threshold;
+  },
+
+  distance: new Point(0, 0),
+  isPan: function cp_isPan() {
+    return (Math.abs(this.distance.x) > this.threshold ||
+            Math.abs(this.distance.y) > this.threshold);
+  },
+
+  _startAnimation: function kp_startAnimation() {
+    let c = kExponentialC;
+    function getNextPosition(position, v, a, t) {
+      // Important traits for this function:
+      //   p(t=0) is 0
+      //   p'(t=0) is v0
+      //
+      // We use exponential to get a smoother stop, but by itself exponential
+      // is too smooth at the end. Adding a polynomial with the appropriate
+      // weight helps to balance
+      position.set(v.x * Math.exp(-t / c) * -c + a.x * t * t + v.x * c,
+                   v.y * Math.exp(-t / c) * -c + a.y * t * t + v.y * c);
+    }
+
+    let startTime = content.mozAnimationStartTime;
+    let elapsedTime = 0, targetedTime = 0, averageTime = 0;
+
+    let velocity = this._velocity;
+    let acceleration = this._acceleration;
+
+    let position = this._position;
+    let nextPosition = new Point(0, 0);
+    let delta = new Point(0, 0);
+
+    let callback = (function(timestamp) {
+      if (!this.target)
+        return;
+
+      // To make animation end fast enough but to keep smoothness, average the
+      // ideal time frame (smooth animation) with the actual time lapse
+      // (end fast enough).
+      // Animation will never take longer than 2 times the ideal length of time.
+      elapsedTime = timestamp - startTime;
+      targetedTime += kUpdateInterval;
+      averageTime = (targetedTime + elapsedTime) / 2;
+
+      // Calculate new position.
+      getNextPosition(nextPosition, velocity, acceleration, averageTime);
+      delta.set(Math.round(nextPosition.x - position.x),
+                Math.round(nextPosition.y - position.y));
+
+      // Test to see if movement is finished for each component.
+      if (delta.x * acceleration.x > 0)
+        delta.x = position.x = velocity.x = acceleration.x = 0;
+
+      if (delta.y * acceleration.y > 0)
+        delta.y = position.y = velocity.y = acceleration.y = 0;
+
+      if (velocity.equals(0, 0) || delta.equals(0, 0)) {
+        this.stop();
+        return;
+      }
+
+      position.add(delta);
+      if (this.target.onKineticPan(delta.scale(-1))) {
+        this.stop();
+        return;
+      }
+
+      content.mozRequestAnimationFrame(callback);
+    }).bind(this);
+
+    content.mozRequestAnimationFrame(callback);
+  }
+};
+
+const ElementTouchHelper = {
+  anyElementFromPoint: function(aWindow, aX, aY) {
+    let cwu = aWindow.QueryInterface(Ci.nsIInterfaceRequestor).getInterface(Ci.nsIDOMWindowUtils);
+    let elem = cwu.elementFromPoint(aX, aY, true, true);
+
+    let HTMLIFrameElement = Ci.nsIDOMHTMLIFrameElement;
+    let HTMLFrameElement = Ci.nsIDOMHTMLFrameElement;
+    while (elem && (elem instanceof HTMLIFrameElement || elem instanceof HTMLFrameElement)) {
+      let rect = elem.getBoundingClientRect();
+      aX -= rect.left;
+      aY -= rect.top;
+      cwu = elem.contentDocument.defaultView.QueryInterface(Ci.nsIInterfaceRequestor).getInterface(Ci.nsIDOMWindowUtils);
+      elem = cwu.elementFromPoint(aX, aY, true, true);
+    }
+
+    return elem;
+  },
+
+  getBoundingContentRect: function(aElement) {
+    if (!aElement)
+      return {x: 0, y: 0, w: 0, h: 0};
+
+    let document = aElement.ownerDocument;
+    while (document.defaultView.frameElement)
+      document = document.defaultView.frameElement.ownerDocument;
+
+    let cwu = document.defaultView.QueryInterface(Ci.nsIInterfaceRequestor).getInterface(Ci.nsIDOMWindowUtils);
+    let scrollX = {}, scrollY = {};
+    cwu.getScrollXY(false, scrollX, scrollY);
+
+    let r = aElement.getBoundingClientRect();
+
+    // step out of iframes and frames, offsetting scroll values
+    for (let frame = aElement.ownerDocument.defaultView; frame.frameElement && frame != content; frame = frame.parent) {
+      // adjust client coordinates' origin to be top left of iframe viewport
+      let rect = frame.frameElement.getBoundingClientRect();
+      let left = frame.getComputedStyle(frame.frameElement, "").borderLeftWidth;
+      let top = frame.getComputedStyle(frame.frameElement, "").borderTopWidth;
+      scrollX.value += rect.left + parseInt(left);
+      scrollY.value += rect.top + parseInt(top);
+    }
+
+    return {x: r.left + scrollX.value,
+            y: r.top + scrollY.value,
+            w: r.width,
+            h: r.height };
+  }
+};