Allow specifying alternate GN directories for run-perf-tests.

third_party/WebKit/Tools/Scripts/webkitpy/performance_tests/perftestsrunner.py

 # Copyright (C) 2012 Google Inc. 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
@@ skipping 63 matching lines @@
     @staticmethod
     def _parse_args(args=None):
         def _expand_path(option, opt_str, value, parser):
             path = os.path.expandvars(os.path.expanduser(value))
             setattr(parser.values, option.dest, path)
         perf_option_list = [
             optparse.make_option('--debug', action='store_const', const='Debug', dest="configuration",
                                  help='Set the configuration to Debug'),
             optparse.make_option('--release', action='store_const', const='Release', dest="configuration",
                                  help='Set the configuration to Release'),
+            optparse.make_option('-t', '--target', dest='configuration',
+                                 help='Specify the target build subdirectory under src/out/'),
             optparse.make_option("--platform",
                                  help="Specify port/platform being tested (e.g. mac)"),
             optparse.make_option("--chromium",
                                  action="store_const", const='chromium', dest='platform', help='Alias for --platform=chromium'),
             optparse.make_option("--android",
                                  action="store_const", const='android', dest='platform', help='Alias for --platform=android'),
             optparse.make_option("--builder-name",
                                  help=("The name of the builder shown on the waterfall running this script e.g. google-mac-2.")),
             optparse.make_option("--build-number",
                                  help=("The build number of the builder running this script.")),
@@ skipping 277 matching lines @@
             if metrics:
                 self._results.append((test, metrics))
             else:
                 failures += 1
                 _log.error('FAILED')
 
             _log.info('Finished: %f s' % (time.time() - start_time))
             _log.info('')
 
         return failures