PPAPI: Make PPP_MessageHandler work in PNaCl

ppapi/api/ppp_message_handler.idl

 /* Copyright 2014 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>PPP_MessageHandler</code> interface that plugins
  * can implement and register using PPB_Messaging::RegisterMessageHandler in
  * order to handle messages sent from JavaScript via postMessage() or
  * postMessageAndAwaitResponse().
  */
 
 label Chrome {
-  [channel=none] M37 = 0.1
+  [channel=dev] M39 = 0.2
 };
 
 /**
  * The <code>PPP_MessageHandler</code> interface is implemented by the plugin
  * if the plugin wants to receive messages from a thread other than the main
  * Pepper thread, or if the plugin wants to handle blocking messages which
  * JavaScript may send via postMessageAndAwaitResponse().
  *
  * This interface struct should not be returned by PPP_GetInterface; instead it
  * must be passed as a parameter to PPB_Messaging::RegisterMessageHandler.
  */
 [no_interface_string]
 interface PPP_MessageHandler {
   /**
    * Invoked as a result of JavaScript invoking postMessage() on the plugin's
    * DOM element.
    *
    * @param[in] instance A <code>PP_Instance</code> identifying one instance
    * of a module.
    * @param[in] user_data is the same pointer which was provided by a call to
    * RegisterMessageHandler.
    * @param[in] message A copy of the parameter that JavaScript provided to
    * postMessage().
    */
   void HandleMessage([in] PP_Instance instance,
                      [inout] mem_t user_data,
-                     [in] PP_Var message);
+                     [constptr_in] PP_Var message);
   /**
    * Invoked as a result of JavaScript invoking postMessageAndAwaitResponse()
    * on the plugin's DOM element.
    *
    * @param[in] instance A <code>PP_Instance</code> identifying one instance
    * of a module.
    * @param[in] user_data is the same pointer which was provided by a call to
    * RegisterMessageHandler.
    * @param[in] message is a copy of the parameter that JavaScript provided
    * to postMessageAndAwaitResponse.
-   * @return will be copied to a JavaScript object which is returned as
-   * the result of postMessageAndAwaitResponse to the invoking JavaScript.
+   * @param[out] response will be copied to a JavaScript object which is
+   * returned as the result of postMessageAndAwaitResponse to the invoking
+     JavaScript.
    */
-  PP_Var HandleBlockingMessage([in] PP_Instance instance,
-                               [inout] mem_t user_data,
-                               [in] PP_Var message);
+  void HandleBlockingMessage([in] PP_Instance instance,
+                             [inout] mem_t user_data,
+                             [constptr_in] PP_Var message,
+                             [out] PP_Var response);
   /**
    * Invoked when the handler object is no longer needed. After this, no more
    * calls will be made which pass this same value for <code>instance</code>
    * and <code>user_data</code>.
    *
    * @param[in] instance A <code>PP_Instance</code> identifying one instance
    * of a module.
    * @param[in] user_data is the same pointer which was provided by a call to
    * RegisterMessageHandler.
    */
   void Destroy([in] PP_Instance instance, [inout] mem_t user_data);
 };