Use a direct include of the message_loop header in chrome/browser/, part 7.

chrome/browser/nacl_host/nacl_process_host.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 "chrome/browser/nacl_host/nacl_process_host.h"
 
 #include <algorithm>
 #include <string>
 #include <vector>
 
 #include "base/base_switches.h"
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/file_util.h"
-#include "base/message_loop.h"
+#include "base/message_loop/message_loop.h"
 #include "base/metrics/histogram.h"
 #include "base/path_service.h"
 #include "base/process_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/win/windows_version.h"
 #include "build/build_config.h"
@@ skipping 886 matching lines @@
   } else {
     NaClStartDebugExceptionHandlerThread(
         process_handle.Take(), info,
         base::MessageLoopProxy::current(),
         base::Bind(&NaClProcessHost::OnDebugExceptionHandlerLaunchedByBroker,
                    weak_factory_.GetWeakPtr()));
     return true;
   }
 }
 #endif