Added a ResourceMessageFilter for handling resource messages on another thread.

ppapi/host/resource_message_handler.cc

Index: ppapi/host/resource_message_handler.cc
diff --git a/ppapi/host/resource_message_handler.cc b/ppapi/host/resource_message_handler.cc
new file mode 100644
index 0000000000000000000000000000000000000000..aaaecc6b3d74af34b4098fbc43287a72f379a9b6
--- /dev/null
+++ b/ppapi/host/resource_message_handler.cc
@@ -0,0 +1,54 @@
+// 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.
+
+#include "ppapi/host/resource_message_handler.h"
+
+#include "ipc/ipc_message.h"
+#include "ppapi/c/pp_errors.h"
+#include "ppapi/host/host_message_context.h"
+
+namespace ppapi {
+namespace host {
+
+ResourceMessageHandler::ResourceMessageHandler() {
+}
+
+ResourceMessageHandler::~ResourceMessageHandler() {
+}
+
+void ResourceMessageHandler::RunMessageHandlerAndReply(
+    const IPC::Message& msg,
+    HostMessageContext* context) {
+  ReplyMessageContext reply_context = context->MakeReplyMessageContext();
+  reply_context.params.set_result(OnResourceMessageReceived(msg, context));
+
+  // Sanity check the resource handler. Note if the result was
+  // "completion pending" the resource host may have already sent the reply.
+  if (reply_context.params.result() == PP_OK_COMPLETIONPENDING) {
+    // Message handler should have only returned a pending result if a
+    // response will be sent to the plugin.
+    DCHECK(context->params.has_callback());
+
+    // Message handler should not have written a message to be returned if
+    // completion is pending.
+    DCHECK(context->reply_msg.type() == 0);
+  } else if (!context->params.has_callback()) {
+    // When no response is required, the message handler should not have
+    // written a message to be returned.
+    DCHECK(context->reply_msg.type() == 0);
+  }
+
+  if (context->params.has_callback() &&
+      reply_context.params.result() != PP_OK_COMPLETIONPENDING)
+    SendReply(reply_context, context->reply_msg);
+}
+
+int32_t ResourceMessageHandler::OnResourceMessageReceived(
+    const IPC::Message& msg,
+    HostMessageContext* context) {
+  return PP_ERROR_NOTSUPPORTED;
+}
+
+}  // namespace host
+}  // namespace ppapi