Implement active wheel fling transfer via WebCompositorInputHandlerClient

content/renderer/gpu/compositor_thread.h

Index: content/renderer/gpu/compositor_thread.h
diff --git a/content/renderer/gpu/compositor_thread.h b/content/renderer/gpu/compositor_thread.h
index ea506d15c31e60675061e86bbbaf683978ff9cfb..91a6e67b8d3e8700e34cee56dcb136d8bf737aee 100644
--- a/content/renderer/gpu/compositor_thread.h
+++ b/content/renderer/gpu/compositor_thread.h
@@ -31,7 +31,7 @@ class CompositorThread {
   // to the compositor's thread.
   IPC::ChannelProxy::MessageFilter* GetMessageFilter() const;
 
-  // Callable from the main thread or the compositor's thread.
+  // Callable from the main thread only.
   void AddInputHandler(int routing_id, int input_handler_id);
 
   webkit_glue::WebThreadImpl* GetWebThread() { return &thread_; }
@@ -44,6 +44,12 @@ class CompositorThread {
   void HandleInputEvent(int routing_id,
                         const WebKit::WebInputEvent* input_event);
 
+  // Called from the compositor's thread.
+  void AddInputHandlerOnCompositorThread(
+      int routing_id,
+      int input_handler_id,
+      scoped_refptr<base::MessageLoopProxy> main_loop);
+
   class InputHandlerWrapper;
   friend class InputHandlerWrapper;