add xvfb

tools/testing/frogpad/frogpad.py

 #!/usr/bin/env python
 
 # Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 #
 
 """
 Frogpad is used to compile .dart files to javascript.
 
@@ skipping 217 matching lines @@
 
   def generate_js(self):
     drt = os.path.join(self.dart_dir, "client/tests/drt/DumpRenderTree")
     if platform.system() == 'Darwin':
       drt += ".app"
     elif platform.system() == 'Windows':
       raise Exception("frogpad does not run on Windows")
 
     check_exists(drt)
     args = []
+    args.append("xvfb-run")
+    args.append("-a")
     args.append(drt)
     args.append(self.html_file)
 
     stdout = run_command(args)
     match = OUTPUT_JAVASCRIPT_REGEX.match(stdout)
     if not match:
       raise Exception("can't find regex in DumpRenderTree output")
     return match.group(1)
 
   @staticmethod
@@ skipping 111 matching lines @@
     raise CommandFailedException(msg)
   logging.debug("SUCCEEDED (%d bytes)" % len(stdout))
   return stdout
 
 
 def main(argv):
   Pad(argv)
 
 if __name__ == "__main__":
   sys.exit(main(sys.argv))