IDL: Autogenerate thunk .cc file for PPB_Messaging.

ppapi/api/ppb_messaging.idl

 /* Copyright (c) 2012 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.
  */
 
 /**
  * This file defines the <code>PPB_Messaging</code> interface implemented
  * by the browser for sending messages to DOM elements associated with a
  * specific module instance.
  */
 
+[generate_thunk]
+
 label Chrome {
   M14 = 1.0
 };
 
 /**
  * The <code>PPB_Messaging</code> interface is implemented by the browser
  * and is related to sending messages to JavaScript message event listeners on
  * the DOM element associated with specific module instance.
  */
 interface PPB_Messaging {
@@ skipping 48 matching lines @@
    *  ppb_messaging_interface->PostMessage(instance, hello_var); // Copies var.
    *  ppb_var_interface->Release(hello_var);
    *
    * @endcode
    *
    * The browser will pop-up an alert saying "Hello world!"
    */
   void PostMessage([in] PP_Instance instance, [in] PP_Var message);
 };