Ensure nacl_integration does not report UMA stats.

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 255 matching lines @@
 
   def MakeCmd(self, url, port):
     cmd = [self.binary,
             '--disable-web-resources',
             '--disable-preconnect',
             '--no-first-run',
             '--no-default-browser-check',
             '--enable-logging',
             '--log-level=1',
             '--safebrowsing-disable-auto-update',
+            # Suppress metrics reporting.

[Mark Seaborn, 2013/01/09 00:20:36]

Add more explanation?  Maybe "Suppress metrics (UMA) reporting so that buildbot
runs do not skew the UMA statistics".

Add the "no known issues" comment here too?

+            '--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
             # Unfortunately, the browser tester can randomly choose a
             # blacklisted port.  To work around this, the tester whitelists
             # whatever port it is using.
             '--explicitly-allowed-ports=%d' % port,
             '--user-data-dir=%s' % self.profile]
     # Log network requests to assist debugging.
     cmd.append('--log-net-log=%s' % self.NetLogName())
@@ skipping 34 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