Move IPC::MessageFilter and router to a separate file

ipc/message_filter_router.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_ROUTER_H_
+#define IPC_MESSAGE_FILTER_ROUTER_H_
+
+#include <vector>
+
+#include "ipc/ipc_message_start.h"
+
+namespace IPC {
+
+class Message;
+class MessageFilter;
+
+class MessageFilterRouter {
+ public:
+  typedef std::vector<MessageFilter*> MessageFilters;
+
+  MessageFilterRouter();
+  ~MessageFilterRouter();
+
+  void AddFilter(MessageFilter* filter);
+  void RemoveFilter(MessageFilter* filter);
+  bool TryFilters(const Message& message);
+  void Clear();
+
+ private:
+  // List of global and selective filters; a given filter will exist in either
+  // |message_global_filters_| OR |message_class_filters_|, but not both.
+  // Note that |message_global_filters_| will be given first offering of any
+  // given message.  It's the filter implementer and installer's
+  // responsibility to ensure that a filter is either global or selective to
+  // ensure proper message filtering order.
+  MessageFilters global_filters_;
+  MessageFilters message_class_filters_[LastIPCMsgStart];
+};
+
+}  // namespace IPC
+
+#endif  // IPC_MESSAGE_FILTER_ROUTER_H_