Move IPC::MessageFilter and router to a separate file

content/child/child_histogram_message_filter.cc

 // Copyright (c) 2012 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_histogram_message_filter.h"
 
 #include <ctype.h>
 
 #include "base/bind.h"
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/histogram_delta_serialization.h"
 #include "content/child/child_process.h"
 #include "content/child/child_thread.h"
 #include "content/common/child_process_messages.h"
+#include "ipc/ipc_channel.h"
 
 namespace content {
 
 ChildHistogramMessageFilter::ChildHistogramMessageFilter()
     : channel_(NULL),
       io_message_loop_(ChildProcess::current()->io_message_loop_proxy()) {
 }
 
 ChildHistogramMessageFilter::~ChildHistogramMessageFilter() {
 }
@@ skipping 36 matching lines @@
   histogram_delta_serialization_->PrepareAndSerializeDeltas(&deltas);
   channel_->Send(
       new ChildProcessHostMsg_ChildHistogramData(sequence_number, deltas));
 
   static int count = 0;
   count++;
   DHISTOGRAM_COUNTS("Histogram.ChildProcessHistogramSentCount", count);
 }
 
 }  // namespace content