[Benchmark] Update Ignition benchmarks to --ignition-staging

tools/perf/benchmarks/v8_helper.py

 # Copyright 2016 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.
 
 _JS_FLAGS_SWITCH = '--js-flags='
 
 
 def EnableIgnition(options):
-  AppendJSFlags(options, '--ignition')
+  AppendJSFlags(options, '--ignition-staging')
 
 
 def AppendJSFlags(options, js_flags):
   existing_js_flags = ''
   # There should be only one occurence of --js-flags in the browser flags. When
   # there are multiple flags, only one of them would be used. Append any
   # additional js_flags to the existing flags (if present).
   for extra_arg in options.extra_browser_args:
     if extra_arg.startswith(_JS_FLAGS_SWITCH):
       # Find and remove the set of existing js_flags.
       existing_js_flags = extra_arg[len(_JS_FLAGS_SWITCH):]
       options.extra_browser_args.remove(extra_arg)
       break
 
   options.AppendExtraBrowserArgs([
       # Add a new --js-flags which includes previous flags.
       '%s%s %s' %  (_JS_FLAGS_SWITCH, js_flags, existing_js_flags)
   ])