PPAPI: Add dev synchronous JS->Plugin messaging API

ppapi/proxy/ppapi_messages.h

 // 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.
 
 // Multiply-included message header, no traditional include guard.
 #include <map>
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
@@ skipping 599 matching lines @@
                     ppapi::ViewData /* new_data */,
                     PP_Bool /* flash_fullscreen */)
 IPC_MESSAGE_ROUTED2(PpapiMsg_PPPInstance_DidChangeFocus,
                     PP_Instance /* instance */,
                     PP_Bool /* has_focus */)
 IPC_MESSAGE_ROUTED3(PpapiMsg_PPPInstance_HandleDocumentLoad,
     PP_Instance /* instance */,
     int /* pending_loader_host_id */,
     ppapi::URLResponseInfoData /* response */)
 
-// PPP_Messaging.
+// PPP_Messaging and PPP_MessageHandler.
 IPC_MESSAGE_ROUTED2(PpapiMsg_PPPMessaging_HandleMessage,
                     PP_Instance /* instance */,
                     ppapi::proxy::SerializedVar /* message */)
+IPC_SYNC_MESSAGE_ROUTED(PpapiMsg_PPPMessageHandler_HandleBlockingMessage,
+                        PP_Instance /* instance */,
+                        ppapi::proxy::SerializedVar /* message */,
+                        ppapi::proxy::SerializedVar /* response */);
 
 // PPP_MouseLock.
 IPC_MESSAGE_ROUTED1(PpapiMsg_PPPMouseLock_MouseLockLost,
                     PP_Instance /* instance */)
 
 // PPP_Pdf
 IPC_MESSAGE_ROUTED2(PpapiMsg_PPPPdf_Rotate,
                     PP_Instance /* instance */,
                     bool /* clockwise */)
 
@@ skipping 1473 matching lines @@
 IPC_MESSAGE_CONTROL1(PpapiHostMsg_Talk_RequestPermission,
                      PP_TalkPermission /* permission */)
 IPC_MESSAGE_CONTROL0(PpapiPluginMsg_Talk_RequestPermissionReply)
 IPC_MESSAGE_CONTROL0(PpapiHostMsg_Talk_StartRemoting)
 IPC_MESSAGE_CONTROL0(PpapiPluginMsg_Talk_StartRemotingReply)
 IPC_MESSAGE_CONTROL0(PpapiHostMsg_Talk_StopRemoting)
 IPC_MESSAGE_CONTROL0(PpapiPluginMsg_Talk_StopRemotingReply)
 IPC_MESSAGE_CONTROL1(PpapiPluginMsg_Talk_NotifyEvent, PP_TalkEvent /* event */)
 
 #endif  // !defined(OS_NACL) && !defined(NACL_WIN64)