nacl_integration: disable DNS prefetching and sync.

ppapi/native_client/tools/browser_tester/browsertester/browserlauncher.py

 #!/usr/bin/python
 # Copyright (c) 2012 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 os.path
 import re
 import shutil
 import sys
 import tempfile
@@ skipping 253 matching lines @@
   def NetLogName(self):
     return os.path.join(self.profile, 'netlog.json')
 
   def MakeCmd(self, url, port):
     cmd = [self.binary,
             # Note that we do not use "--enable-logging" here because
             # it actually turns off logging to the Buildbot logs on
             # Windows (see http://crbug.com/169941).
             '--disable-web-resources',
             '--disable-preconnect',
+            # This is speculative, sync should not occur with a clean profile.
+            '--disable-sync',
+            # This prevents Chrome from making "hidden" network requests at
+            # startup.  These requests could be a source of non-determinism,
+            # and they also add noise to the netlogs.
+            '--dns-prefetch-disable',
             '--no-first-run',
             '--no-default-browser-check',
             '--log-level=1',
             '--safebrowsing-disable-auto-update',
             # Suppress metrics reporting.  This prevents misconfigured bots,
             # people testing at their desktop, etc from poisoning the UMA data.
             '--metrics-recording-only',
             # Chrome explicitly blacklists some ports as "unsafe" because
             # certain protocols use them.  Chrome gives an error like this:
             # Error 312 (net::ERR_UNSAFE_PORT): Unknown error
@@ skipping 43 matching lines @@
              '--trace-children=yes',
              '--nacl-file=%s' % (self.options.files[0],),
              '--ignore=../tools/valgrind/tsan/ignores.txt',
              '--suppressions=../tools/valgrind/tsan/suppressions.txt',
              '--log-file=%s/log.%%p' % (self.tool_log_dir,)] + cmd
     elif self.options.tool != None:
       raise LaunchFailure('Invalid tool name "%s"' % (self.options.tool,))
     cmd.extend(self.options.browser_flags)
     cmd.append(url)
     return cmd