Introduce MessageFilterHost for Pepper ResourceHosts.

ppapi/host/message_filter_host.cc

+// 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/message_filter_host.h"
+
+#include "ppapi/host/ppapi_host.h"
+#include "ppapi/host/resource_message_filter.h"
+
+namespace ppapi {
+namespace host {
+
+MessageFilterHost::MessageFilterHost(
+    PpapiHost* host,
+    PP_Instance instance,
+    PP_Resource resource,
+    const scoped_refptr<ResourceMessageFilter>& message_filter)
+    : ResourceHost(host, instance, resource) {
+  AddFilter(message_filter);
+}
+
+MessageFilterHost::~MessageFilterHost() {
+}
+
+}  // namespace host
+}  // namespace ppapi