Make SingleThreadProxy a SchedulerClient

content/renderer/render_widget.h

Index: content/renderer/render_widget.h
diff --git a/content/renderer/render_widget.h b/content/renderer/render_widget.h
index 3084e92ba9d82d0f5ae52e6331e8fcb762c45f81..2c928fc6c72093d2c3cd74956205610838a30b31 100644
--- a/content/renderer/render_widget.h
+++ b/content/renderer/render_widget.h
@@ -162,6 +162,9 @@ class CONTENT_EXPORT RenderWidget
   // Begins the compositor's scheduler to start producing frames.
   void StartCompositor();
 
+  // Stop compositing.
+  void DestroyLayerTreeView();
+
   // Called when a plugin is moved.  These events are queued up and sent with
   // the next paint or scroll message to the host.
   void SchedulePluginMove(const WebPluginGeometry& move);
@@ -590,6 +593,9 @@ class CONTENT_EXPORT RenderWidget
   // be sent, except for a Close.
   bool closing_;
 
+  // True if it is known that the host is in the process of being shut down.
+  bool host_closing_;
+
   // Whether this RenderWidget is currently swapped out, such that the view is
   // being rendered by another process.  If all RenderWidgets in a process are
   // swapped out, the process can exit.