Create a PPAPI host for new resource message routing.

ppapi/host/host_message_context.h

Index: ppapi/host/host_message_context.h
diff --git a/ppapi/host/host_message_context.h b/ppapi/host/host_message_context.h
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+// 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.
+
+#ifndef PPAPI_COMMON_HOST_MESSAGE_CONTEXT_H_
+#define PPAPI_COMMON_HOST_MESSAGE_CONTEXT_H_
+
+#include "ipc/ipc_message.h"
+#include "ppapi/host/ppapi_host_export.h"
+#include "ppapi/proxy/resource_message_params.h"
+
+namespace ppapi {
+namespace host {
+
+// This context structure provides information about incoming resource message
+// call requests when passed to resources.
+struct PPAPI_HOST_EXPORT HostMessageContext {
+  explicit HostMessageContext(const ppapi::proxy::ResourceMessageCallParams& cp)
+      : params(cp) {
+  }
+
+  // The original call parameters passed to the resource message call.
+  const ppapi::proxy::ResourceMessageCallParams& params;
+
+  // The reply message. If the params has the callback flag set, this message
+  // will be sent in reply. It is initialized to the empty message. If the
+  // handler wants to send something else, it should just assign the message
+  // it wants to this value.
+  IPC::Message reply_msg;
+};
+
+}  // namespace host
+}  // namespace ppapi
+
+#endif  // PPAPI_COMMON_HOST_MESSAGE_CONTEXT_H_