Move IPC::MessageFilter and router to a separate file

ipc/ipc_message_filter.cc

+// Copyright (c) 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.
+
+#include "ipc/ipc_message_filter.h"
+
+#include "base/memory/ref_counted.h"
+#include "ipc/ipc_channel.h"
+
+namespace IPC {
+
+MessageFilter::MessageFilter() {}
+
+void MessageFilter::OnFilterAdded(Channel* channel) {}
+
+void MessageFilter::OnFilterRemoved() {}
+
+void MessageFilter::OnChannelConnected(int32 peer_pid) {}
+
+void MessageFilter::OnChannelError() {}
+
+void MessageFilter::OnChannelClosing() {}
+
+bool MessageFilter::OnMessageReceived(const Message& message) {
+  return false;
+}
+
+bool MessageFilter::GetSupportedMessageClasses(
+    std::vector<uint32>* /*supported_message_classes*/) const {
+  return false;
+}
+
+MessageFilter::~MessageFilter() {}
+
+}  // namespace IPC