Turning the threaded compositor into a runtime option. This CL

content/renderer/render_widget.h

Index: content/renderer/render_widget.h
===================================================================
--- content/renderer/render_widget.h	(revision 104391)
+++ content/renderer/render_widget.h	(working copy)
@@ -323,6 +323,10 @@
   // just handled.
   virtual void DidHandleTouchEvent(const WebKit::WebTouchEvent& event) {}
 
+  // Should return true if the underlying WebWidget is responsible for
+  // the scheduling of compositing requests.
+  virtual bool WebWidgetHandlesCompositorScheduling() const;
+
   // Routing ID that allows us to communicate to the parent browser process
   // RenderWidgetHost. When MSG_ROUTING_NONE, no messages may be sent.
   int32 routing_id_;