Speculative fix for flakines on browser bots

tools/testing/run_selenium.py

 #!/usr/bin/python
 
 # Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 #
 
 """Script to actually open a browser and perform the test, and reports back with
 the result. It uses Selenium WebDriver when possible for running the tests. It
 uses Selenium RC for Safari.
@@ skipping 68 matching lines @@
 
   if isinstance(browser, selenium.selenium):
     return run_test_in_browser_selenium_rc(browser, html_out, timeout, mode,
         refresh)
 
   browser.get(html_out)
   if refresh:
     browser.refresh()
   try:
     def pythonTimeout():
-      close_browser(browser)
+      # The builtin quit call for chrome will call close on the RemoteDriver
+      # which may hang. Explicitly call browser.service.stop()
+      if (type(browser) is selenium.webdriver.chrome.webdriver.WebDriver):
+        # Browser may be dead
+        try:
+          browser.service.stop()
+        except:
+          print("Trying to close browser that has already been closed")
     # If the browser is crashing selenium may not time out.
     # Explicitly catch this case with a python timer.
     t = threading.Timer(timeout, pythonTimeout)
     t.start()
     test_done = CONFIGURATIONS[mode]
     element = WebDriverWait(browser, float(timeout)).until(
         lambda driver: test_done(driver.page_source))
     t.cancel()
     return browser.page_source
   except selenium.common.exceptions.TimeoutException:
@@ skipping 130 matching lines @@
     return
   if isinstance(browser, selenium.selenium):
     browser.stop()
     return
 
   # A timeout exception is thrown if nothing happens within the time limit.
   if (type(browser) is not selenium.webdriver.chrome.webdriver.WebDriver and
       type(browser) is not selenium.webdriver.ie.webdriver.WebDriver):
     browser.close()
 
-  # The builtin quit call will call close on the RemoteDriver which
-  # may hang. Explicitly call browser.service.stop()
-  if (type(browser) is selenium.webdriver.chrome.webdriver.WebDriver):
-    # We may have called stop before if chrome was hanging.
-    try:
-      browser.service.stop()
-    except:
-      print("Trying to close browser that has already been closed")
-      pass
-  else:
-    browser.quit()
+  browser.quit()
 
 def report_results(mode, source, browser):
   # TODO(vsm): Add a failure check for Dromaeo.
   if mode != 'correctness':
     # We're running a performance test.
     print source.encode('utf8')
     sys.stdout.flush()
     if 'NaN' in source:
       return 1
     else:
@@ skipping 130 matching lines @@
   browser = start_browser(browser_name, executable_path, html_out)
 
   try:
     output = run_test_in_browser(browser, html_out, timeout, mode, refresh)
     return report_results(mode, output, browser)
   finally:
     close_browser(browser)
 
 if __name__ == "__main__":
   sys.exit(main(sys.argv))