Added a ResourceMessageFilter for handling resource messages on another thread.

ppapi/host/host_message_context.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.
 
 #ifndef PPAPI_HOST_HOST_MESSAGE_CONTEXT_H_
 #define PPAPI_HOST_HOST_MESSAGE_CONTEXT_H_
 
 #include "ipc/ipc_message.h"
 #include "ppapi/host/ppapi_host_export.h"
 #include "ppapi/proxy/resource_message_params.h"
@@ skipping 27 matching lines @@
   explicit HostMessageContext(
       const ppapi::proxy::ResourceMessageCallParams& cp);
   HostMessageContext(
       const ppapi::proxy::ResourceMessageCallParams& cp,
       IPC::Message* sync_reply_msg);
   ~HostMessageContext();
 
   // Returns a reply message context struct which includes the reply params.
   ReplyMessageContext MakeReplyMessageContext() const;
 
-  // The original call parameters passed to the resource message call.
-  const ppapi::proxy::ResourceMessageCallParams& params;
+  // The original call parameters passed to the resource message call. This
+  // cannot be a reference because this object may be passed to another thread.
+  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;
 
   // If this context is generated from a sync message, this will be set to the
   // incoming sync message. Otherwise, it will be NULL.
   IPC::Message* sync_reply_msg;
 };
 
 }  // namespace host
 }  // namespace ppapi
 
 #endif  // PPAPI_HOST_HOST_MESSAGE_CONTEXT_H_