BrowserOptions.extra_browser_args is now a set.

tools/perf/measurements/blink_perf.py

 # Copyright (c) 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.
 
 """This measurement runs a blink performance test and reports the results."""
 
 import os
 import sys
 
 from telemetry.core import util
@@ skipping 63 matching lines @@
     return CreatePageSetFromPath(page_set_arg)
 
   @property
   def results_are_the_same_on_every_page(self):
     return False
 
   def WillNavigateToPage(self, page, tab):
     page.script_to_evaluate_on_commit = self._blink_perf_js
 
   def CustomizeBrowserOptions(self, options):
-    options.AppendExtraBrowserArg('--js-flags=--expose_gc')
-    options.AppendExtraBrowserArg('--enable-experimental-web-platform-features')
+    options.AppendExtraBrowserArgs([
+        '--js-flags=--expose_gc',
+        '--enable-experimental-web-platform-features'
+    ])
 
   def MeasurePage(self, page, tab, results):
     def _IsDone():
       return tab.EvaluateJavaScript('testRunner.isDone')
     util.WaitFor(_IsDone, 600)
 
     log = tab.EvaluateJavaScript('document.getElementById("log").innerHTML')
 
     for line in log.splitlines():
       if not line.startswith('values '):
         continue
       parts = line.split()
       values = [float(v.replace(',', '')) for v in parts[1:-1]]
       units = parts[-1]
       metric = page.display_name.split('.')[0].replace('/', '_')
       results.Add(metric, units, values)
       break
 
     print log