cc: Refactor how picture layers are exposed to the tile manager.

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 9609ccf3e449f282ec504f6e35a1001d5a4a93cc..be1ee348f83e35625310fc49123cf1e4b7718942 100644
--- a/cc/layers/picture_layer_impl.h
+++ b/cc/layers/picture_layer_impl.h
@@ -132,10 +132,10 @@ class CC_EXPORT PictureLayerImpl
   virtual void RunMicroBenchmark(MicroBenchmarkImpl* benchmark) OVERRIDE;
 
   // Functions used by tile manager.
-  void DidUnregisterLayer();
   PictureLayerImpl* GetTwinLayer() { return twin_layer_; }
   WhichTree GetTree() const;
   bool IsOnActiveOrPendingTree() const;
+  bool HasValidTilePriorities() const;
   bool AllTilesRequiredForActivationAreReadyToDraw() const;
 
  protected:
@@ -207,8 +207,6 @@ class CC_EXPORT PictureLayerImpl
   // after a CalculateContentsScale/ManageTilings.
   bool should_update_tile_priorities_;
 
-  bool layer_needs_to_register_itself_;
-
   // Save a copy of the visible rect and viewport size of the last frame that
   // has a valid viewport for prioritizing tiles.
   gfx::Rect visible_rect_for_tile_priority_;