PPAPI: Move PPB_Messaging 1.2 to stable

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.
  */
 
 label Chrome {
   M14 = 1.0,
-  [channel=dev] M39 = 1.2
+  M39 = 1.2
 };
 
 /**
  * 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 {
   /**
    * PostMessage() asynchronously invokes any listeners for message events on
@@ skipping 110 matching lines @@
    * Attempting to unregister a message handler when none is registered has no
    * effect.
    *
    * @param[in] instance A <code>PP_Instance</code> identifying one instance
    * of a module.
    */
   [version=1.2]
   void UnregisterMessageHandler([in] PP_Instance instance);
 };