cc: Block commit on activate by setting a flag on LayerTreeHost.

cc/layers/layer.h

Index: cc/layers/layer.h
diff --git a/cc/layers/layer.h b/cc/layers/layer.h
index b659ab265546a3a64b813baebc66afd6f98963df..71f6c2c09d1b12532dda42f492ab2b4187102126 100644
--- a/cc/layers/layer.h
+++ b/cc/layers/layer.h
@@ -397,13 +397,6 @@ class CC_EXPORT Layer : public base::RefCounted<Layer>,
 
   gfx::Rect LayerRectToContentRect(const gfx::RectF& layer_rect) const;
 
-  // In impl-side painting, this returns true if this layer type is not
-  // compatible with the main thread running freely, such as a double-buffered
-  // canvas that doesn't want to be triple-buffered across all three trees.
-  virtual bool BlocksPendingCommit() const;
-  // Returns true if anything in this tree blocksPendingCommit.
-  bool BlocksPendingCommitRecursive() const;
-
   virtual skia::RefPtr<SkPicture> GetPicture() const;
 
   virtual bool CanClipSelf() const;
@@ -455,7 +448,11 @@ class CC_EXPORT Layer : public base::RefCounted<Layer>,
   // Called when there's been a change in layer structure.  Implies both
   // SetNeedsUpdate and SetNeedsCommit, but not SetNeedsPushProperties.
   void SetNeedsFullTreeSync();
-  bool IsPropertyChangeAllowed() const;
+
+  // Called when the next commit should wait until the pending tree is activated
+  // before finishing the commit and unblocking the main thread. Used to ensure
+  // unused resources on the impl thread are returned before commit completes.
+  void SetNextCommitWaitsForActivation();
 
   void SetNeedsPushProperties();
   void AddDependentNeedsPushProperties();
@@ -464,6 +461,8 @@ class CC_EXPORT Layer : public base::RefCounted<Layer>,
     return needs_push_properties() || descendant_needs_push_properties();
   }
 
+  bool IsPropertyChangeAllowed() const;
+
   // If this layer has a scroll parent, it removes |this| from its list of
   // scroll children.
   void RemoveFromScrollTree();