Remove message_loop_helpers.h and update the includes to point to the new location.

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 203 matching lines @@
           '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.cc',
           'message_loop.h',
-          'message_loop_helpers.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',
@@ skipping 380 matching lines @@
           ['<(chromeos)!=1 or >(nacl_untrusted_build)==1', {
             'sources/': [
               ['exclude', '^chromeos/'],
             ],
           }],
         ],
       }],
     ],
   },
 }