cc: ReadyToDraw notifications.

cc/trees/layer_tree_host_impl.h

Index: cc/trees/layer_tree_host_impl.h
diff --git a/cc/trees/layer_tree_host_impl.h b/cc/trees/layer_tree_host_impl.h
index 51ef8b01a0315871045a73ca6ae9ec68ff2267bd..1dee0769b1e0cd8b0f81b3c4ed4bf92fd9a2b94e 100644
--- a/cc/trees/layer_tree_host_impl.h
+++ b/cc/trees/layer_tree_host_impl.h
@@ -76,6 +76,7 @@ class LayerTreeHostImplClient {
   virtual void DidSwapBuffersCompleteOnImplThread() = 0;
   virtual void OnCanDrawStateChanged(bool can_draw) = 0;
   virtual void NotifyReadyToActivate() = 0;
+  virtual void NotifyReadyToDraw() = 0;
   // Please call these 3 functions through
   // LayerTreeHostImpl's SetNeedsRedraw(), SetNeedsRedrawRect() and
   // SetNeedsAnimate().
@@ -238,6 +239,7 @@ class CC_EXPORT LayerTreeHostImpl
   virtual const std::vector<PictureLayerImpl*>& GetPictureLayers()
       const override;
   virtual void NotifyReadyToActivate() override;
+  virtual void NotifyReadyToDraw() override;
   virtual void NotifyTileStateChanged(const Tile* tile) override;
   virtual void BuildRasterQueue(RasterTilePriorityQueue* queue,
                                 TreePriority tree_priority) override;