Introduce content::ChildMessageFilter.

content/child/child_message_filter.cc

+// Copyright 2013 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 "content/child/child_message_filter.h"
+
+#include "content/child/child_thread.h"
+#include "content/child/thread_safe_sender.h"
+
+namespace content {
+
+class ChildMessageFilter::Internal : public IPC::ChannelProxy::MessageFilter {
+ public:
+  explicit Internal(ChildMessageFilter* filter) : filter_(filter) {}
+
+  // IPC::ChannelProxy::MessageFilter overrides.
+  virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE {
+    scoped_refptr<base::TaskRunner> runner =
+        filter_->OverrideTaskRunnerForMessage(message);
+    if (runner) {
+      runner->PostTask(
+          FROM_HERE,
+          base::Bind(base::IgnoreResult(&ChildMessageFilter::OnMessageReceived),
+                     filter_,
+                     message));
+      return true;
+    }
+
+    return filter_->OnMessageReceived(message);
+  }
+
+ private:
+  virtual ~Internal() {}
+
+  ChildMessageFilter* filter_;  // Avoid circular references.
+
+  DISALLOW_COPY_AND_ASSIGN(Internal);
+};
+
+ChildMessageFilter::ChildMessageFilter()
+    : internal_(new Internal(this)),
+      thread_safe_sender_(ChildThread::current()->thread_safe_sender()) {}
+
+ChildMessageFilter::~ChildMessageFilter() {}
+
+bool ChildMessageFilter::Send(IPC::Message* message) {
+  return thread_safe_sender_->Send(message);
+}
+
+base::TaskRunner* ChildMessageFilter::OverrideTaskRunnerForMessage(
+    const IPC::Message& message) {
+  return NULL;
+}
+
+}  // namespace content