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 1fc0989bbb103dc07ab9e6146c4d0891443b2963..39c294626599fc88cbb5bbd400ddb859fe29072b 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().
@@ -235,6 +236,7 @@ class CC_EXPORT LayerTreeHostImpl
   // TileManagerClient implementation.
   const std::vector<PictureLayerImpl*>& GetPictureLayers() const override;
   void NotifyReadyToActivate() override;
+  void NotifyReadyToDraw() override;
   void NotifyTileStateChanged(const Tile* tile) override;
   void BuildRasterQueue(RasterTilePriorityQueue* queue,
                         TreePriority tree_priority) override;