cc: ReadyToDraw notifications.

cc/layers/picture_layer_impl.h

Index: cc/layers/picture_layer_impl.h
diff --git a/cc/layers/picture_layer_impl.h b/cc/layers/picture_layer_impl.h
index 1ac106a7c1bce10fe0bddfbc3b5c46d1ae6a1684..ace7b71c3fcffed9b2ab3258c5b43773d9624710 100644
--- a/cc/layers/picture_layer_impl.h
+++ b/cc/layers/picture_layer_impl.h
@@ -149,6 +149,7 @@ class CC_EXPORT PictureLayerImpl
   // Virtual for testing.
   virtual bool HasValidTilePriorities() const;
   bool AllTilesRequiredForActivationAreReadyToDraw() const;
+  bool AllTilesRequiredForDrawAreReadyToDraw() const;
 
  protected:
   friend class LayerRasterTileIterator;
@@ -179,6 +180,12 @@ class CC_EXPORT PictureLayerImpl
   bool CanHaveTilings() const;
   bool CanHaveTilingWithScale(float contents_scale) const;
   void SanityCheckTilingState() const;
+  // Checks if all tiles required for a certain action (e.g. activation) are
+  // ready to draw.  is_tile_required_callback gets called on all candidate
+  // tiles and returns true if the tile is required for the action.
+  bool AllTilesRequiredAreReadyToDraw(
+      const base::Callback<bool(PictureLayerTiling* tiling, const Tile*)>&
+          is_tile_required_callback) const;
 
   bool ShouldAdjustRasterScaleDuringScaleAnimations() const;