PPAPI: Add dev synchronous JS->Plugin messaging API

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
+  M14 = 1.0,
+  [channel=dev] M36 = 1.1
 };
 
 /**
  * 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 48 matching lines @@
    *  PP_Var hello_var = ppb_var_interface->VarFromUtf8(instance,
    *                                                    hello_world,
    *                                                    sizeof(hello_world));
    *  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!"
    */
+  [version=1.0]
   void PostMessage([in] PP_Instance instance, [in] PP_Var message);
+
+  /**
+   * Registers a handler for receiving messages from JavaScript. If a handler
+   * is registered this way, it will replace PPP_Messaging, and all messages
+   * sent from JavaScript via postMessage and postMessageAndAwaitResponse will
+   * be dispatched to <code>handler</code>.
+   *
+   * The function calls will be dispatched via <code>message_loop</code>. This
+   * means that the functions will be invoked on the thread to which
+   * <code>message_loop</code> is attached, when <code>message_loop</code> is
+   * run. It is illegal to pass the main thread message loop;
+   * RegisterMessageHandler will return PP_ERROR_WRONG_THREAD in that case.
+   *
+   * Attempting to register a message handler when one is already registered
+   * will cause the current MessageHandler to be unregistered and replaced. In
+   * that case, no messages will be sent to the "default" message handler
+   * (PPP_Messaging). Messages will stop arriving at the prior message handler
+   * and will begin to be dispatched at the new message handler.
+   *
+   * @param[in] instance A <code>PP_Instance</code> identifying one instance
+   * of a module.
+   * @param[in] user_data A pointer the plugin may choose to use when handling
+   * calls to functions within PPP_MessageHandler. The browser will pass this
+   * same pointer when invoking functions within PPP_MessageHandler.
+   * @param[in] handler The plugin-provided set of functions for handling
+   * messages.
+   * @param[in] message_loop represents the message loop on which
+   * PPP_MessageHandler functions should be invoked.
+   * @return PP_OK on success, or an error from pp_errors.h.
+   */
+  [version=1.1]
+  int32_t RegisterMessageHandler([in] PP_Instance instance,
+                                 [in] mem_t user_data,
+                                 [in] PPP_MessageHandler handler,
+                                 [in] PP_Resource message_loop);
+  /**
+   * Unregisters the current message handler for <code>instance</code> if one
+   * is registered. After this call, the message handler (if one was
+   * registered) will have "Destroy" called on it and will receive no further
+   * messages after that point. After that point, all messages sent from
+   * JavaScript using postMessage() will be dispatched to PPP_Messaging (if
+   * the plugin supports PPP_MESSAGING_INTERFACE). Attempts to call
+   * postMessageAndAwaitResponse() from JavaScript will fail.
+   *
+   * 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=1.1]
+  void UnregisterMessageHandler([in] PP_Instance instance);
 };