PPAPI: Add C++ wrapper for MessageHandler stuff.

ppapi/c/ppp_message_handler.h

 /* 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.
  */
 
-/* From ppp_message_handler.idl modified Wed Sep 10 17:04:21 2014. */
+/* From ppp_message_handler.idl modified Wed Sep 17 16:54:35 2014. */
 
 #ifndef PPAPI_C_PPP_MESSAGE_HANDLER_H_
 #define PPAPI_C_PPP_MESSAGE_HANDLER_H_
 
 #include "ppapi/c/pp_bool.h"
 #include "ppapi/c/pp_instance.h"
 #include "ppapi/c/pp_macros.h"
 #include "ppapi/c/pp_stdint.h"
 #include "ppapi/c/pp_var.h"
 
@@ skipping 20 matching lines @@
  * must be passed as a parameter to PPB_Messaging::RegisterMessageHandler.
  */
 struct PPP_MessageHandler_0_2 { /* dev */
   /**
    * 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.
+   * RegisterMessageHandler().
    * @param[in] message A copy of the parameter that JavaScript provided to
    * postMessage().
    */
   void (*HandleMessage)(PP_Instance instance,
                         void* user_data,
                         const struct PP_Var* message);
   /**
    * Invoked as a result of JavaScript invoking postMessageAndAwaitResponse()
    * on the plugin's DOM element.
    *
+   * NOTE: JavaScript execution is blocked during the duration of this call.
+   * Hence, the plugin should respond as quickly as possible. For this reason,
+   * blocking completion callbacks are disallowed while handling a blocking
+   * message.
+   *
    * @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.
+   * RegisterMessageHandler().
    * @param[in] message is a copy of the parameter that JavaScript provided
-   * to postMessageAndAwaitResponse.
+   * to postMessageAndAwaitResponse().
    * @param[out] response will be copied to a JavaScript object which is
-   * returned as the result of postMessageAndAwaitResponse to the invoking
+   * returned as the result of postMessageAndAwaitResponse() to the invoking
    *
    */
   void (*HandleBlockingMessage)(PP_Instance instance,
                                 void* user_data,
                                 const struct PP_Var* message,
                                 struct 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)(PP_Instance instance, void* user_data);
 };
 /**
  * @}
  */
 
 #endif  /* PPAPI_C_PPP_MESSAGE_HANDLER_H_ */