Fetch the first tab inside the browser startup retry loop.

content/test/gpu/gpu_tests/pixel_integration_test.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 glob
 import logging
 import os
 import re
 import sys
 
 from gpu_tests import cloud_storage_integration_test_base
@@ skipping 76 matching lines @@
   @classmethod
   def RestartBrowserIfNecessaryWithArgs(cls, browser_args):
     if not browser_args:
       browser_args = []
     if set(browser_args) != cls._last_launched_browser_args:
       logging.warning('Restarting browser with arguments: ' + str(browser_args))
       cls.StopBrowser()
       cls.ResetGpuInfo()
       cls.CustomizeBrowserArgs(browser_args)
       cls.StartBrowser()
-      cls.tab = cls.browser.tabs[0]
 
   @classmethod
   def AddCommandlineArgs(cls, parser):
     super(PixelIntegrationTest, cls).AddCommandlineArgs(parser)
     parser.add_option(
       '--reference-dir',
       help='Overrides the default on-disk location for reference images '
       '(only used for local testing without a cloud storage account)',
       default=default_reference_image_dir)
 
@@ skipping 112 matching lines @@
       ref_png = None
 
     if ref_png is not None:
       return ref_png
 
     print ('Reference image not found. Writing tab contents as reference to: ' +
            image_path)
 
     self._WriteImage(image_path, screenshot)
     return screenshot