Don't use PostTask queueing between compositor and main thread.

content/renderer/input/input_handler_manager_client.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_RENDERER_INPUT_INPUT_HANDLER_MANAGER_CLIENT_H_
 #define CONTENT_RENDERER_INPUT_INPUT_HANDLER_MANAGER_CLIENT_H_
 
 #include "base/callback.h"
 #include "base/callback_forward.h"
 #include "base/macros.h"
@@ skipping 24 matching lines @@
   // The Manager will supply a |handler| when bound to the client. This is valid
   // until the manager shuts down, at which point it supplies a null |handler|.
   // The client should only makes calls to |handler| on the compositor thread.
   typedef base::Callback<
       InputEventAckState(int /*routing_id*/,
                          const blink::WebInputEvent*,
                          ui::LatencyInfo* latency_info)> Handler;
 
   // Called from the main thread.
   virtual void SetBoundHandler(const Handler& handler) = 0;
+  virtual void NotifyInputEventHandled(int routing_id,
+                                       blink::WebInputEvent::Type type,
+                                       InputEventAckState ack_result) = 0;
 
   // Called from the compositor thread.
   virtual void RegisterRoutingID(int routing_id) = 0;
   virtual void UnregisterRoutingID(int routing_id) = 0;
   virtual void DidOverscroll(int routing_id,
                              const DidOverscrollParams& params) = 0;
   virtual void DidStartFlinging(int routing_id) = 0;
   virtual void DidStopFlinging(int routing_id) = 0;
-  virtual void NotifyInputEventHandled(int routing_id,
-                                       blink::WebInputEvent::Type type,
-                                       InputEventAckState ack_result) = 0;
 
  protected:
   InputHandlerManagerClient() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(InputHandlerManagerClient);
 };
 
 class CONTENT_EXPORT SynchronousInputHandlerProxyClient {
  public:
   virtual ~SynchronousInputHandlerProxyClient() {}
 
   virtual void DidAddSynchronousHandlerProxy(
       int routing_id,
       ui::SynchronousInputHandlerProxy* synchronous_handler) = 0;
   virtual void DidRemoveSynchronousHandlerProxy(int routing_id) = 0;
 
  protected:
   SynchronousInputHandlerProxyClient() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(SynchronousInputHandlerProxyClient);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_INPUT_INPUT_HANDLER_MANAGER_CLIENT_H_