Move IPC::MessageFilter and router to a separate file

ipc/message_filter.h

+// Copyright 2014 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 IPC_MESSAGE_FILTER_H_
+#define IPC_MESSAGE_FILTER_H_
+
+#include <vector>
+
+#include "base/memory/ref_counted.h"
+#include "ipc/ipc_export.h"
+
+namespace IPC {
+
+class Channel;
+class Message;
+
+// A class that receives messages on the thread where the IPC channel is
+// running.  It can choose to prevent the default action for an IPC message.
+class IPC_EXPORT MessageFilter
+    : public base::RefCountedThreadSafe<MessageFilter> {
+ public:
+  MessageFilter();
+
+  // Called on the background thread to provide the filter with access to the
+  // channel.  Called when the IPC channel is initialized or when AddFilter
+  // is called if the channel is already initialized.
+  virtual void OnFilterAdded(Channel* channel);
+
+  // Called on the background thread when the filter has been removed from
+  // the ChannelProxy and when the Channel is closing.  After a filter is
+  // removed, it will not be called again.
+  virtual void OnFilterRemoved();
+
+  // Called to inform the filter that the IPC channel is connected and we
+  // have received the internal Hello message from the peer.
+  virtual void OnChannelConnected(int32 peer_pid);
+
+  // Called when there is an error on the channel, typically that the channel
+  // has been closed.
+  virtual void OnChannelError();
+
+  // Called to inform the filter that the IPC channel will be destroyed.
+  // OnFilterRemoved is called immediately after this.
+  virtual void OnChannelClosing();
+
+  // Return true to indicate that the message was handled, or false to let
+  // the message be handled in the default way.
+  virtual bool OnMessageReceived(const Message& message);
+
+  // Called to query the Message classes supported by the filter.  Return
+  // false to indicate that all message types should reach the filter, or true
+  // if the resulting contents of |supported_message_classes| may be used to
+  // selectively offer messages of a particular class to the filter.
+  virtual bool GetSupportedMessageClasses(
+      std::vector<uint32>* supported_message_classes) const;
+
+ protected:
+  virtual ~MessageFilter();
+
+ private:
+  friend class base::RefCountedThreadSafe<MessageFilter>;
+};
+
+}  // namespace IPC
+
+#endif  // IPC_MESSAGE_FILTER_H_