Make MessageLoopProxy::current() usable on threads that don't have MessageLoop.

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 328 matching lines @@
           'sys_info_posix.cc',
           'sys_info_win.cc',
           'sys_string_conversions.h',
           'sys_string_conversions_mac.mm',
           'sys_string_conversions_posix.cc',
           'sys_string_conversions_win.cc',
           'task_runner.cc',
           'task_runner.h',
           'task_runner_util.h',
           'template_util.h',
+          'thread_main_task_runner.cc',
+          'thread_main_task_runner.h',
           'threading/non_thread_safe.h',
           'threading/non_thread_safe_impl.cc',
           'threading/non_thread_safe_impl.h',
           'threading/platform_thread.h',
           'threading/platform_thread_mac.mm',
           'threading/platform_thread_posix.cc',
           'threading/platform_thread_win.cc',
           'threading/post_task_and_reply_impl.cc',
           'threading/post_task_and_reply_impl.h',
           'threading/sequenced_worker_pool.cc',
@@ skipping 569 matching lines @@
             'third_party/xdg_mime/xdgmimemagic.c',
             'third_party/xdg_mime/xdgmimemagic.h',
             'third_party/xdg_mime/xdgmimeparent.c',
             'third_party/xdg_mime/xdgmimeparent.h',
           ],
         },
       ],
     }],
   ],
 }