cc: Add a flag to layers that returns true if the layer is in RSLL.

cc/trees/layer_tree_impl.h

Index: cc/trees/layer_tree_impl.h
diff --git a/cc/trees/layer_tree_impl.h b/cc/trees/layer_tree_impl.h
index bc488db3c54c7bf96bc4edf7b8e479841695be49..be53d19c951daf4dec6c7232f733efc697a29435 100644
--- a/cc/trees/layer_tree_impl.h
+++ b/cc/trees/layer_tree_impl.h
@@ -244,6 +244,10 @@ class CC_EXPORT LayerTreeImpl {
   void RemoveLayerWithCopyOutputRequest(LayerImpl* layer);
   const std::vector<LayerImpl*>& LayersWithCopyOutputRequest() const;
 
+  int current_render_surface_list_id() const {
+    return render_surface_layer_list_id_;
+  }
+
  protected:
   explicit LayerTreeImpl(LayerTreeHostImpl* layer_tree_host_impl);
 
@@ -297,6 +301,8 @@ class CC_EXPORT LayerTreeImpl {
 
   UIResourceRequestQueue ui_resource_request_queue_;
 
+  int render_surface_layer_list_id_;
+
  private:
   DISALLOW_COPY_AND_ASSIGN(LayerTreeImpl);
 };