Create a new base/message_loop directory and move the message_loop_proxy.

base/base.gypi

 # 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.
 
 {
   'target_defaults': {
     'variables': {
       'base_target': 0,
     },
     'target_conditions': [
@@ skipping 258 matching lines @@
           'memory/scoped_handle.h',
           'memory/scoped_nsobject.h',
           'memory/scoped_open_process.h',
           'memory/scoped_policy.h',
           'memory/scoped_ptr.h',
           'memory/scoped_vector.h',
           'memory/singleton.cc',
           'memory/singleton.h',
           'memory/weak_ptr.cc',
           'memory/weak_ptr.h',
+          'message_loop/message_loop_proxy.cc',
+          'message_loop/message_loop_proxy.h',
+          'message_loop/message_loop_proxy_impl.cc',
+          'message_loop/message_loop_proxy_impl.h',
           'message_loop.cc',
           'message_loop.h',
-          'message_loop_proxy.cc',
-          'message_loop_proxy.h',
-          'message_loop_proxy_impl.cc',
-          'message_loop_proxy_impl.h',
           'message_pump.cc',
           'message_pump.h',
           'message_pump_android.cc',
           'message_pump_android.h',
           'message_pump_default.cc',
           'message_pump_default.h',
           'message_pump_win.cc',
           'message_pump_win.h',
           'metrics/sample_map.cc',
           'metrics/sample_map.h',
@@ skipping 469 matching lines @@
           ['<(use_system_nspr)==1 and >(nacl_untrusted_build)==0', {
             'sources/': [
               ['exclude', '^third_party/nspr/'],
             ],
           }],
         ],
       }],
     ],
   },
 }