diff -r 000000000000 -r 6474c204b198 gfx/layers/apz/src/TaskThrottler.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gfx/layers/apz/src/TaskThrottler.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,63 @@
+/* -*- Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 8; -*- */
+/* vim: set sw=2 sts=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 "TaskThrottler.h"
+
+namespace mozilla {
+namespace layers {
+
+TaskThrottler::TaskThrottler(const TimeStamp& aTimeStamp)
+  : mOutstanding(false)
+  , mQueuedTask(nullptr)
+  , mStartTime(aTimeStamp)
+  , mMean(1)
+{ }
+
+void
+TaskThrottler::PostTask(const tracked_objects::Location& aLocation,
+                        CancelableTask* aTask, const TimeStamp& aTimeStamp)
+{
+  aTask->SetBirthPlace(aLocation);
+
+  if (mOutstanding) {
+    if (mQueuedTask) {
+      mQueuedTask->Cancel();
+    }
+    mQueuedTask = aTask;
+  } else {
+    mStartTime = aTimeStamp;
+    aTask->Run();
+    delete aTask;
+    mOutstanding = true;
+  }
+}
+
+void
+TaskThrottler::TaskComplete(const TimeStamp& aTimeStamp)
+{
+  if (!mOutstanding) {
+    return;
+  }
+
+  mMean.insert(aTimeStamp - mStartTime);
+
+  if (mQueuedTask) {
+    mStartTime = aTimeStamp;
+    mQueuedTask->Run();
+    mQueuedTask = nullptr;
+  } else {
+    mOutstanding = false;
+  }
+}
+
+TimeDuration
+TaskThrottler::TimeSinceLastRequest(const TimeStamp& aTimeStamp)
+{
+  return aTimeStamp - mStartTime;
+}
+
+}
+}