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 ff912a4b9bb0d17d0a9e38c681cbbfdf9b3eedd4..0fb5f5f284354a108ddd6e9804ec708edc006afe 100644
--- a/cc/trees/layer_tree_impl.h
+++ b/cc/trees/layer_tree_impl.h
@@ -243,6 +243,10 @@ 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);
 
@@ -296,6 +300,8 @@ class CC_EXPORT LayerTreeImpl {
 
   UIResourceRequestQueue ui_resource_request_queue_;
 
+  int render_surface_layer_list_id_;
+
  private:
   DISALLOW_COPY_AND_ASSIGN(LayerTreeImpl);
 };