PPAPI: Add dev synchronous JS->Plugin messaging API

ppapi/proxy/ppapi_messages.h

Index: ppapi/proxy/ppapi_messages.h
diff --git a/ppapi/proxy/ppapi_messages.h b/ppapi/proxy/ppapi_messages.h
index e099b36709f4f179bbe684adc8ae80c08d766860..4ef8c50de9e551f848a29a7f3c2bd2cbee3418fa 100644
--- a/ppapi/proxy/ppapi_messages.h
+++ b/ppapi/proxy/ppapi_messages.h
@@ -617,10 +617,14 @@ IPC_MESSAGE_ROUTED3(PpapiMsg_PPPInstance_HandleDocumentLoad,
     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,

[Tom Sepez, 2014/05/07 22:27:10]

Don't you mean IPC_SYNC_MESSAGE_ROUTED2_1?

[dmichael (off chromium), 2014/05/30 20:30:46]

Removed from this CL. The implementation CL will add the new message...
https://codereview.chromium.org/264303002/

+                        PP_Instance /* instance */,
+                        ppapi::proxy::SerializedVar /* message */,
+                        ppapi::proxy::SerializedVar /* response */);
 
 // PPP_MouseLock.
 IPC_MESSAGE_ROUTED1(PpapiMsg_PPPMouseLock_MouseLockLost,