Switch run_perf.py to use positional arguments for extra_flags.

scripts/slave/recipe_modules/v8/api.py

 # Copyright 2013 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 collections
 import datetime
 import math
 import re
 import urllib
 
@@ skipping 1026 matching lines @@
       ]
 
       if out_dir_no_patch:
         full_args.extend([
           '--outdir-no-patch', out_dir_no_patch,
           '--json-test-results-no-patch',
           self.m.json.output(add_json_log=False),
         ])
 
       if extra_flags:
-        full_args.append('--extra-flags="%s"' % ' '.join(extra_flags))
+        full_args.extend(['--extra-flags', ' '.join(extra_flags)])
 
       full_args.append(json_file)
 
       def step_test_data():
         test_data = self.test_api.perf_json(
             self._test_data.get('perf_failures', False))
         if out_dir_no_patch:
           return test_data + self.test_api.perf_improvement_json()
         else:
           return test_data
@@ skipping 207 matching lines @@
   def report_culprits(self, culprit_range):
     assert culprit_range
     if len(culprit_range) > 1:
       text = 'Suspecting multiple commits'
     else:
       text = 'Suspecting %s' % culprit_range[0][:8]
 
     step_result = self.m.python.inline(text, '# Empty program')
     for culprit in culprit_range:
       step_result.presentation.links[culprit[:8]] = COMMIT_TEMPLATE % culprit