predictors: Move the configuration of speculative prefetch to field trials.

tools/resource_prefetch_predictor/prefetch_benchmark.py

 #!/usr/bin/python
 #
 # 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.
 
 """Loads a web page with speculative prefetch, and collects loading metrics."""
 
 import argparse
 import logging
@@ skipping 16 matching lines @@
 
 sys.path.append(os.path.join(_SRC_PATH, 'build', 'android'))
 import devil_chromium
 
 sys.path.append(os.path.join(_SRC_PATH, 'third_party', 'catapult', 'devil'))
 from devil.android.sdk import intent
 
 import prefetch_predictor_common
 
 
-_EXTERNAL_PREFETCH_FLAG = (
-    '--speculative-resource-prefetching=enabled-external-only')
-
-
 def _CreateArgumentParser():
   """Creates and returns the argument parser."""
   parser = argparse.ArgumentParser(
       ('Loads a URL with the resource_prefetch_predictor and prints loading '
        'metrics.'), parents=[OPTIONS.GetParentParser()])
   parser.add_argument('--device', help='Device ID')
   parser.add_argument('--database',
                       help=('File containing the predictor database, as '
                             'obtained from generate_database.py.'))
   parser.add_argument('--url', help='URL to load.')
@@ skipping 16 matching lines @@
   chrome_package = OPTIONS.ChromePackage()
   device.ForceStop(chrome_package.package)
   chrome_controller.ResetBrowserState()
   device_database_filename = prefetch_predictor_common.DatabaseDevicePath()
   owner = group = None
 
   # Make sure that the speculative prefetch predictor is enabled to ensure
   # that the disk database is re-created.
   command_line_path = '/data/local/tmp/chrome-command-line'
   with device_setup.FlagReplacer(
-      device, command_line_path, ['--disable-fre', _EXTERNAL_PREFETCH_FLAG]):
+      device, command_line_path, ['--disable-fre']):
     # Launch Chrome for the first time to recreate the local state.
     launch_intent = intent.Intent(
         action='android.intent.action.MAIN',
         package=chrome_package.package,
         activity=chrome_package.activity)
     device.StartActivity(launch_intent, blocking=True)
     time.sleep(5)
     device.ForceStop(chrome_package.package)
     assert device.FileExists(device_database_filename)
     stats = device.StatPath(device_database_filename)
@@ skipping 65 matching lines @@
   while True:
     delay = delays[random.randint(0, len(delays) - 1)]
     _RunOnce(device, args.database, args.url, delay, args.output_filename,
              args.wpr_archive, args.network_condition)
     if args.once:
       return
 
 
 if __name__ == '__main__':
   main()