Fetch the first tab inside the browser startup retry loop.

content/test/gpu/gpu_tests/gpu_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 logging
 
 from telemetry.testing import serially_executed_browser_test_case
 from telemetry.util import screenshot
 
 from gpu_tests import exception_formatter
@@ skipping 10 matching lines @@
     for test_name, url, args in cls.GenerateGpuTests(options):
       yield test_name, (url, test_name, args)
 
   @classmethod
   def StartBrowser(cls):
     for x in range(0, 3):
       try:
         restart = 'Starting browser, attempt %d of 3' % (x + 1)
         logging.warning(restart)
         super(GpuIntegrationTest, cls).StartBrowser()
+        cls.tab = cls.browser.tabs[0]
+        logging.warning('Started browser successfully.')
         return
       except Exception:
         # If we are on the last try and there is an exception take a screenshot
         # to try and capture more about the browser failure and raise
         if x == 2:
           url = screenshot.TryCaptureScreenShotAndUploadToCloudStorage(
             cls.platform)
           if url is not None:
             logging.info("GpuIntegrationTest screenshot of browser failure " +
               "located at " + url)
           else:
             logging.warning("GpuIntegrationTest unable to take screenshot")
           raise
+        # Otherwise, stop the browser to make sure it's in an
+        # acceptable state to try restarting it.
+        if cls.browser:
+          cls.StopBrowser()
 
   @classmethod
   def _RestartBrowser(cls, reason):
     logging.warning('Restarting browser due to '+ reason)
     cls.StopBrowser()
     cls.SetBrowserOptions(cls._finder_options)
     cls.StartBrowser()
-    cls.tab = cls.browser.tabs[0]
 
   def _RunGpuTest(self, url, test_name, *args):
     expectations = self.__class__.GetExpectations()
     expectation = expectations.GetExpectationForTest(
       self.browser, url, test_name)
     if expectation == 'skip':
       # skipTest in Python's unittest harness raises an exception, so
       # aborts the control flow here.
       self.skipTest('SKIPPING TEST due to test expectations')
     try:
@@ skipping 120 matching lines @@
       cls.tab = cls.browser.tabs[0]
     except Exception:
       # restart the browser to make sure a failure in a test doesn't
       # propagate to the next test iteration.
       logging.exception("Failure during browser startup")
       cls._RestartBrowser('failure in setup')
       raise
 
   def setUp(self):
     self._EnsureTabIsAvailable()