Enable native custom elements for Pica benchmark

R=tonyg@chromium.org
BUG=245358

Review URL: https://codereview.chromium.org/22884003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@217042 0039d316-1c4b-4281-b951-d872f2087c98

tools/perf/benchmarks/pica.py

@@ -6,6 +6,10 @@ from telemetry import test
 from telemetry.page import page_measurement
 
 class PicaMeasurement(page_measurement.PageMeasurement):
+  def CustomizeBrowserOptions(self, options):
+    # Needed for native custom elements (document.register)
+    options.AppendExtraBrowserArg('--enable-experimental-web-platform-features')
+
   def MeasurePage(self, _, tab, results):
     result = int(tab.EvaluateJavaScript('__pica_load_time'))
     results.Add('Total', 'ms', result)