PPAPI: Implement synchronous postMessage

ppapi/proxy/message_handler.h

Index: ppapi/proxy/message_handler.h
diff --git a/ppapi/proxy/message_handler.h b/ppapi/proxy/message_handler.h
new file mode 100644
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+++ b/ppapi/proxy/message_handler.h
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+// 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.
+
+#ifndef PPAPI_PROXY_MESSAGE_HANDLER_H_
+#define PPAPI_PROXY_MESSAGE_HANDLER_H_
+
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "ppapi/c/pp_resource.h"
+#include "ppapi/c/ppp_message_handler.h"
+#include "ppapi/proxy/ppapi_proxy_export.h"
+
+namespace IPC {
+class Message;
+}
+
+namespace ppapi {
+
+class ScopedPPVar;
+
+namespace proxy {
+
+class MessageLoopResource;
+
+// MessageHandler wraps a PPP_MessageHandler to encapsulate calling methods
+// on the right thread and calling the Destroy function when this
+// MessageHandler is destroyed.
+class PPAPI_PROXY_EXPORT MessageHandler {
+ public:
+  // Create a MessageHandler. If any parameters are invalid, it will return a
+  // null scoped_ptr and set |*error| appropriately.
+  // |handler_if| is the struct of function pointers we will invoke. All of
+  //              the function pointers within must be valid, or we fail
+  //              with PP_ERROR_BADARGUMENT.
+  // |user_data| is a pointer provided by the plugin that we pass back when we
+  //             call functions in |handler_if|.
+  // |message_loop| is the message loop where we will invoke functions in
+  //                |handler_if|. Must not be the main thread message loop,
+  //                to try to force the plugin to not over-subscribe the main
+  //                thread. If it's the main thread loop, |error| will be set
+  //                to PP_ERROR_WRONGTHREAD.
+  // |error| is an out-param that will be set on failure.
+  static scoped_ptr<MessageHandler> Create(
+      PP_Instance instance,
+      const PPP_MessageHandler_0_1* handler_if,
+      void* user_data,
+      PP_Resource message_loop,
+      int32_t* error);
+  ~MessageHandler();
+
+  bool LoopIsValid() const;
+
+  void HandleMessage(ScopedPPVar var);
+  void HandleBlockingMessage(ScopedPPVar var,
+                             scoped_ptr<IPC::Message> reply_msg);
+
+ private:
+  MessageHandler(PP_Instance instance,
+                 const PPP_MessageHandler_0_1* handler_if,
+                 void* user_data,
+                 scoped_refptr<MessageLoopResource> message_loop);
+
+  PP_Instance instance_;
+  const PPP_MessageHandler_0_1* handler_if_;
+  void* user_data_;
+  scoped_refptr<MessageLoopResource> message_loop_;
+
+  DISALLOW_COPY_AND_ASSIGN(MessageHandler);
+};
+
+}  // namespace proxy
+}  // namespace ppapi
+
+#endif  // PPAPI_PROXY_MESSAGE_HANDLER_H_