Make fast tls the default

tools/gyp/v8.gyp

 # Copyright 2011 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 45 matching lines @@
 
     'v8_use_snapshot%': 'true',
     'host_os%': '<(OS)',
     'v8_use_liveobjectlist%': 'false',
   },
   'conditions': [
     ['use_system_v8==0', {
       'target_defaults': {
         'defines': [
           'ENABLE_DEBUGGER_SUPPORT',
-          'V8_FAST_TLS',
         ],
         'conditions': [
           ['OS!="mac"', {
             # TODO(mark): The OS!="mac" conditional is temporary. It can be
             # removed once the Mac Chromium build stops setting target_arch to
             # ia32 and instead sets it to mac. Other checks in this file for
             # OS=="mac" can be removed at that time as well. This can be cleaned
             # up once http://crbug.com/44205 is fixed.
             'conditions': [
               ['v8_target_arch=="arm"', {
@@ skipping 928 matching lines @@
           'type': 'none',
           'toolsets': ['host'],
           'dependencies': [
             'v8'
           ],
         },
       ],
     }],
   ],
 }