Add --use-osmesa flag to skydb

sky/tools/skydb

 #!/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.
 
 import argparse
 import os
 import subprocess
 import sys
 import urlparse
@@ skipping 47 matching lines @@
                 str(HTTP_PORT),
             ]
             self._sky_server = subprocess.Popen(server_command)
         return 'http://localhost:%s/%s' % (HTTP_PORT, relative_path)
 
     def main(self):
         logging.basicConfig(level=logging.INFO)
 
         parser = argparse.ArgumentParser(description='Sky launcher/debugger')
         parser.add_argument('--gdb', action='store_true')
+        parser.add_argument('--use-osmesa', action='store_true')
         parser.add_argument('url', nargs='?', type=str)
         args = parser.parse_args()
 
         content_handlers = ['%s,%s' % (mime_type, 'mojo://sky_viewer/')
             for mime_type in SUPPORTED_MIME_TYPES]
         shell_command = [
             MOJO_SHELL_PATH,
             '--v=1',
             '--content-handlers=%s' % ','.join(content_handlers),
             '--url-mappings=mojo:window_manager=mojo:sky_debugger',
             'mojo:window_manager',
         ]
         if args.url:
             url = args.url
             if not urlparse.urlparse(url).scheme:
                 url = self._start_http_server_for_file(url)
 
             prompt_args = '--args-for=mojo://sky_debugger_prompt/ %s' % url
             shell_command.append(prompt_args)
+        if args.use_osmesa:
+            shell_command.append('--args-for=mojo://native_viewport_service/ --use-osmesa')
         if args.gdb:
             shell_command = ['gdb', '--args'] + shell_command
 
         subprocess.check_call(shell_command)
 
     def shutdown(self):
         print "Quitting"
         if self._sky_server:
             self._sky_server.terminate()
 
 
 if __name__ == '__main__':
     skydb = SkyDebugger()
     try:
         skydb.main()
     except (KeyboardInterrupt, SystemExit):
         pass
     finally:
         skydb.shutdown()