Provide DllMain, and hook to support TLS callbacks.

base/base.gyp

 # Copyright (c) 2011 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.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'includes': [
     '../build/win_precompile.gypi',
@@ skipping 102 matching lines @@
       'type': 'executable',
       'sources': [
         # Infrastructure files.
         'test/run_all_unittests.cc',
 
         # Tests.
         'android/scoped_java_ref_unittest.cc',
         'at_exit_unittest.cc',
         'atomicops_unittest.cc',
         'base64_unittest.cc',
+        'win/dllmain.cc',
         'bind_unittest.cc',
         'bind_unittest.nc',
         'bits_unittest.cc',
         'build_time_unittest.cc',
         'callback_unittest.cc',
         'callback_unittest.nc',
         'cancelable_callback_unittest.cc',
         'command_line_unittest.cc',
         'cpu_unittest.cc',
         'debug/leak_tracker_unittest.cc',
@@ skipping 324 matching lines @@
           'msvs_settings': {
             'VCLinkerTool': {
               'SubSystem': '2',         # Set /SUBSYSTEM:WINDOWS
             },
           },
         },
       ],
     }],
   ],
 }