sandwich: Adds command line flag to disable WPR injections

tools/android/loading/device_setup.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.
 
 import contextlib
 import logging
 import os
 import shutil
 import subprocess
 import sys
@@ skipping 97 matching lines @@
     device.adb.ForwardRemove(local)
 
 
 def _SetUpDevice(device, package_info):
   """Enables root and closes Chrome on a device."""
   device.EnableRoot()
   device.KillAll(package_info.package, quiet=True)
 
 
 @contextlib.contextmanager
-def WprHost(device, wpr_archive_path, record=False):
+def WprHost(device, wpr_archive_path, record=False,
+            disable_script_injection=False):
   """Launches web page replay host.
 
   Args:
     device: Android device.
     wpr_archive_path: host sided WPR archive's path.
     record: Enables or disables WPR archive recording.
 
   Returns:
     Additional flags list that may be used for chromium to load web page through
     the running web page replay host.
   """
   assert device
   if wpr_archive_path == None:
     yield []
     return
 
   wpr_server_args = ['--use_closest_match']
   if record:
     wpr_server_args.append('--record')
     if os.path.exists(wpr_archive_path):
       os.remove(wpr_archive_path)
   else:
     assert os.path.exists(wpr_archive_path)
 
+  if disable_script_injection:
+    # Remove default WPR injected scripts like deterministic.js which
+    # overrides Math.random.
+    wpr_server_args.extend(['--inject_scripts', ''])
+
   # Deploy certification authority to the device.
   temp_certificate_dir = tempfile.mkdtemp()
   wpr_ca_cert_path = os.path.join(temp_certificate_dir, 'testca.pem')
   certutils.write_dummy_ca_cert(*certutils.generate_dummy_ca_cert(),
                                 cert_path=wpr_ca_cert_path)
 
   device_cert_util = adb_install_cert.AndroidCertInstaller(
       device.adb.GetDeviceSerial(), None, wpr_ca_cert_path)
   device_cert_util.install_cert(overwrite_cert=True)
   wpr_server_args.extend(['--should_generate_certs',
@@ skipping 100 matching lines @@
     package: the key for chrome package info.
     fn: the function to execute that launches chrome and performs the
         appropriate instrumentation. The function will receive a
         DevToolsConnection as its sole parameter.
 
   Returns:
     As fn() returns.
   """
   with DeviceConnection(device, package) as connection:
     return fn(connection)