Introduce content::ChildMessageFilter.

content/child/child_message_filter.h

+// 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.
+
+#ifndef CONTENT_CHILD_CHILD_MESSAGE_FILTER_H_
+#define CONTENT_CHILD_CHILD_MESSAGE_FILTER_H_
+
+#include "ipc/ipc_channel_proxy.h"
+
+namespace content {
+
+class ThreadSafeSender;
+
+// Convenience base class for implementing IPC MessageFilters that run on the
+// child thread and can dispatch messages to arbitrary task runners.
+class ChildMessageFilter
+    : public base::RefCountedThreadSafe<ChildMessageFilter>,
+      public IPC::Sender {
+ public:
+  ChildMessageFilter();
+
+  // IPC::Sender implementation.
+  //
+  // Can be called on any thread.
+  virtual bool Send(IPC::Message* message) OVERRIDE;
+
+  // Override to have OnMessageReceived() run on a TaskRunner of your choosing.
+  // Returns NULL by default, which runs OnMessageReceived() on the child
+  // thread.
+  virtual base::TaskRunner* OverrideTaskRunnerForMessage(
+      const IPC::Message& message);
+
+  virtual bool OnMessageReceived(const IPC::Message& message) = 0;

[scherkus (not reviewing), 2013/11/07 21:24:23]

reminder to self: needs docs

+
+ protected:
+  friend class base::RefCountedThreadSafe<ChildMessageFilter>;
+  virtual ~ChildMessageFilter();
+
+ private:
+  class Internal;
+  friend class RenderThreadImpl;
+
+  // Returns private IPC::ChannelProxy::MessageFilter implementation. Intended
+  // for use by friend classes listed above.
+  scoped_refptr<IPC::ChannelProxy::MessageFilter> get_internal() {
+    return internal_;
+  }
+
+  // Private implementation of IPC::ChannelProxy::MessageFilter hidden from
+  // child classes. An equivalent API is provided to child classes.
+  scoped_refptr<IPC::ChannelProxy::MessageFilter> internal_;
+
+  // Used to implement a thread-safe IPC::Sender implementation for child
+  // classes.
+  scoped_refptr<ThreadSafeSender> thread_safe_sender_;
+
+  DISALLOW_COPY_AND_ASSIGN(ChildMessageFilter);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_CHILD_CHILD_MESSAGE_FILTER_H_