import changes from `dev' branch of rmottola/Arctic-Fox:

- Bug 1077651 Measure frame uniformity by synthesizing native events. r=kats,mrbkap (95a796145)
- Bug 1154231 - Part 2. Reclaim cached resources when memory-pressure occurs. r=mattwoodrow (cff6ac1f9)
- fix build (15112d396)
- Bug 1155649 - XFlush at the end of frames when OMTC is enabled on Linux. r=jrmuizel (8bc22dd42)
- Bug 1158120 - Edit include and comments that contained gfxIntSize and nsIntSize. r=nical (fc25c0c96)
- Bug 1167235 - Part 1: Add code exposing a PersistentBufferProvider. r=nical (8340f8ede)
- Bug 1134251 - Disable broken B2G Desktop tests on Mulet. r=jmaher, r=jgilbert (db4d4253c)
- Bug 1134271 - Skip conformance/canvas/buffer-offscreen-test.html on Android; r=jgilbert (2fe8d8623)
- Bug 1124996 - Remove expected fail on OSX 10.10. r=jgilbert (388438a7e)
- Bug 1145492 - Update FramebufferTexture2D to allow binding mipmaps. r=jgilbert (5e4c6bf95)
- Bug 1158089 - Remove LAYERS_D3D10 enum value since it's unused. r=Bas (720d3b3b4)
- Bug 1156058 - Null pointer check. r=jgilbert (f9b9c6ca6)
- Bug 1131463 - Report AtomicRefCounterWithFinalize doing the wrong thing with AddRef and Release in release build as well. r=sotaro (7c009766e)
- Bug 1142071 - Re-add WaitForBufferOwnership() r=jgilbert (0753bcd25)
- partial revert of patch not found... (4ed1e76f1)
- Bug 1143979 - Use RAII local instead of useless temporary. - r=kamidphish (d8a50143f)
- Bug 1017865 - Refactor attach/detach for FB attachments. - r=kamidphish (9c7e41065)
- Bug 1144906 - Add accel E10S backend for WebGL compositing. - r=jrmuizel,mattwoodrow,nical,sotaro (559ab767f)
- Bug 1167235 - Part 2: Add support for the basic buffer provider to CanvasLayer. r=nical (4ac399c16)
- Bug 1155252 - Add a pref to control the maximum canvas 2d size and set it to 0x7ff. r=jrmuizel (7ae6cde3f)
- Bug 1167235 - Part 3: Switch CanvasRenderingContext2D to use the new BufferProvider API. r=nical (f678c14ab)
- Bug 1192159: Do not forget about the transform when not using an active target. r=jrmuizel (a4bd28a75)
- Bug 1167235 - Part 4: Remove DrawTarget as a possible means of initializing Canvas layers. r=nical (dbd153cfb)
- Bug 1167235 - Part 5: Make CanvasLayerComposite ImageHost type agnostic. r=nical (df15bd85d)
- Bug 1167235 - Part 6: Fix up HasInternalBuffer return value on TextureHostDirectUpload. r=nical (437cd1680)
- Bug 1091851 - Fix a race condition in Sqlite.jsm shutdown. r=mak (8b6ac8848)

widget/PuppetWidget.h

@@ -279,6 +279,18 @@ private:
     PuppetWidget* mWidget;
   };
 
+  class MemoryPressureObserver : public nsIObserver {
+  public:
+    NS_DECL_ISUPPORTS
+    NS_DECL_NSIOBSERVER
+    explicit MemoryPressureObserver(PuppetWidget* aWidget) : mWidget(aWidget) {}
+    void Remove();
+  private:
+    virtual ~MemoryPressureObserver() {}
+    PuppetWidget* mWidget;
+  };
+  friend class MemoryPressureObserver;
+
   // TabChild normally holds a strong reference to this PuppetWidget
   // or its root ancestor, but each PuppetWidget also needs a
   // reference back to TabChild (e.g. to delegate nsIWidget IME calls
@@ -291,6 +303,7 @@ private:
   nsRefPtr<PuppetWidget> mChild;
   nsIntRegion mDirtyRegion;
   nsRevocableEventPtr<PaintTask> mPaintTask;
+  nsRefPtr<MemoryPressureObserver> mMemoryPressureObserver;
   // XXX/cjones: keeping this around until we teach LayerManager to do
   // retained-content-only transactions
   mozilla::RefPtr<DrawTarget> mDrawTarget;