Move platform_thread to base/threading and put in the base namespace. I left ...

base/base.gypi

 # Copyright (c) 2010 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 147 matching lines @@
           'object_watcher.h',
           'observer_list.h',
           'observer_list_threadsafe.h',
           'path_service.cc',
           'path_service.h',
           'pickle.cc',
           'pickle.h',
           'platform_file.h',
           'platform_file_posix.cc',
           'platform_file_win.cc',
-          'platform_thread.h',
-          'platform_thread_mac.mm',
-          'platform_thread_posix.cc',
-          'platform_thread_win.cc',
           'port.h',
           'process.h',
           'process_linux.cc',
           'process_posix.cc',
           'process_util.cc',
           'process_util.h',
           'process_util_linux.cc',
           'process_util_mac.mm',
           'process_util_posix.cc',
           'process_util_win.cc',
@@ skipping 54 matching lines @@
           'sys_info_win.cc',
           'sys_string_conversions.h',
           'sys_string_conversions_linux.cc',
           'sys_string_conversions_mac.mm',
           'sys_string_conversions_win.cc',
           'task.cc',
           'task.h',
           'task_queue.cc',
           'task_queue.h',
           'template_util.h',
+          'threading/platform_thread.h',
+          'threading/platform_thread_mac.mm',
+          'threading/platform_thread_posix.cc',
+          'threading/platform_thread_win.cc',
           'threading/simple_thread.cc',
           'threading/simple_thread.h',
+          'threading/thread_checker.cc',
+          'threading/thread_checker.h',
           'threading/thread_local.h',
           'threading/thread_local_posix.cc',
           'threading/thread_local_storage.h',
           'threading/thread_local_storage_posix.cc',
           'threading/thread_local_storage_win.cc',
           'threading/thread_local_win.cc',
           'threading/watchdog.cc',
           'threading/watchdog.h',
           'threading/worker_pool.h',
           'threading/worker_pool_posix.cc',
           'threading/worker_pool_posix.h',
           'threading/worker_pool_win.cc',
           'thread.cc',
           'thread.h',
-          'thread_checker.cc',
-          'thread_checker.h',
           'thread_collision_warner.cc',
           'thread_collision_warner.h',
           'thread_restrictions.h',
           'thread_restrictions.cc',
           'time.cc',
           'time.h',
           'time_win.cc',
           'timer.cc',
           'timer.h',
           'tracked.cc',
@@ skipping 456 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',
           ],
         },
       ],
     }],
   ],
 }