GN bootstrap fixes:

tools/gn/bootstrap/bootstrap.py

 #!/usr/bin/env python
 # Copyright 2014 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.
 
 """Bootstraps gn.
 
 It is done by first building it manually in a temporary directory, then building
 it with its own BUILD.gn to the final destination.
 """
@@ skipping 65 matching lines @@
   parser = optparse.OptionParser(description=sys.modules[__name__].__doc__)
   parser.add_option('-d', '--debug', action='store_true',
                     help='Do a debug build. Defaults to release build.')
   parser.add_option('-o', '--output',
                     help='place output in PATH', metavar='PATH')
   parser.add_option('-s', '--no-rebuild', action='store_true',
                     help='Do not rebuild GN with GN.')
   parser.add_option('--no-clean', action='store_true',
                     help='Re-used build directory instead of using new '
                          'temporary location each time')
+  parser.add_option('--gn-gen-args', help='Args to pass to gn gen --args')
   parser.add_option('-v', '--verbose', action='store_true',
                     help='Log more details')
   options, args = parser.parse_args(argv)
 
   if args:
     parser.error('Unrecognized command line arguments: %s.' % ', '.join(args))
 
   logging.basicConfig(level=logging.DEBUG if options.verbose else logging.ERROR)
 
   try:
@@ skipping 131 matching lines @@
       'base/task_runner.cc',
       'base/third_party/dmg_fp/dtoa_wrapper.cc',
       'base/third_party/dmg_fp/g_fmt.cc',
       'base/third_party/icu/icu_utf.cc',
       'base/third_party/nspr/prtime.cc',
       'base/thread_task_runner_handle.cc',
       'base/threading/non_thread_safe_impl.cc',
       'base/threading/post_task_and_reply_impl.cc',
       'base/threading/sequenced_worker_pool.cc',
       'base/threading/simple_thread.cc',
+      'base/threading/thread.cc',
       'base/threading/thread_checker_impl.cc',
       'base/threading/thread_collision_warner.cc',
       'base/threading/thread_id_name_manager.cc',
       'base/threading/thread_local_storage.cc',
       'base/threading/thread_restrictions.cc',
       'base/threading/worker_pool.cc',
       'base/time/time.cc',
       'base/timer/elapsed_timer.cc',
       'base/timer/timer.cc',
       'base/trace_event/memory_allocator_dump.cc',
@@ skipping 181 matching lines @@
   else:
     ninja_lines.append('  ld = $ldxx')
 
   ninja_lines.append('')  # Make sure the file ends with a newline.
 
   with open(path, 'w') as f:
     f.write(ninja_template + '\n'.join(ninja_lines))
 
 
 def build_gn_with_gn(temp_gn, build_dir, options):
-  cmd = [temp_gn, 'gen', build_dir]
+  gn_gen_args = options.gn_gen_args or ''
   if not options.debug:
-    cmd.append('--args=is_debug=false')
+    gn_gen_args += ' is_debug=false'
+  cmd = [temp_gn, 'gen', build_dir, '--args=%s' % gn_gen_args]
   check_call(cmd)
 
   cmd = ['ninja', '-C', build_dir]
   if options.verbose:
     cmd.append('-v')
   cmd.append('gn')
   check_call(cmd)
 
   if not options.debug:
     check_call(['strip', os.path.join(build_dir, 'gn')])
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))