Update from https://crrev.com/333737

testing/chromoting/browser_tests_launcher.py

 # Copyright (c) 2014 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.
 
 
 """Utility script to launch browser-tests on the Chromoting bot."""
 import argparse
 import glob
 import hashlib
 import os
 from os.path import expanduser
 import shutil
 import socket
 import subprocess
 
 import psutil
 
 BROWSER_TEST_ID = 'browser_tests'
 PROD_DIR_ID = '#PROD_DIR#'
 HOST_HASH_VALUE = hashlib.md5(socket.gethostname()).hexdigest()
 SUCCESS_INDICATOR = 'SUCCESS: all tests passed.'
 NATIVE_MESSAGING_DIR = 'NativeMessagingHosts'
 CRD_ID = 'chrome-remote-desktop'  # Used in a few file/folder names
 CHROMOTING_HOST_PATH = '/opt/google/chrome-remote-desktop/chrome-remote-desktop'
 TEST_FAILURE = False
 FAILING_TESTS = ''
 HOST_READY_INDICATOR = 'Host ready to receive connections.'
+BROWSER_NOT_STARTED_ERROR = (
+    'Still waiting for the following processes to finish')
+TIME_OUT_INDICATOR = '(TIMED OUT)'
+MAX_RETRIES = 1
 
 
-def LaunchBTCommand(command):
+def LaunchBTCommand(args, command):
+  """Launches the specified browser-test command.
+
+      If the execution failed because a browser-instance was not launched, retry
+      once.
+  Args:
+    args: Command line args, used for test-case startup tasks.
+    command: Browser-test command line.
+  """
   global TEST_FAILURE, FAILING_TESTS
-  results = RunCommandInSubProcess(command)
+
+  retries = 0
+  while retries <= MAX_RETRIES:
+    TestCaseSetup(args)
+    results = RunCommandInSubProcess(command)
+
+    if SUCCESS_INDICATOR in results:
+      # Test passed.
+      break
+
+    # Sometimes, during execution of browser-tests, a browser instance is
+    # not started and the test times out. See http://crbug/480025.
+    # To work around it, check if this execution failed owing to that
+    # problem and retry.
+    # There are 2 things to look for in the results:
+    # A line saying "Still waiting for the following processes to finish",
+    # and, because sometimes that line gets logged even if the test
+    # eventually passes, we'll also look for "(TIMED OUT)", before retrying.
+    if not (
+        BROWSER_NOT_STARTED_ERROR in results and TIME_OUT_INDICATOR in results):
+      # Test failed for some other reason. Let's not retry.
+      break
+    retries += 1
 
   # Check that the test passed.
   if SUCCESS_INDICATOR not in results:
     TEST_FAILURE = True
     # Add this command-line to list of tests that failed.
     FAILING_TESTS += command
 
 
 def RunCommandInSubProcess(command):
   """Creates a subprocess with command-line that is passed in.
@@ skipping 123 matching lines @@
 
 def PrintRunningProcesses():
   processes = psutil.get_process_list()
   processes = sorted(processes, key=lambda process: process.name)
 
   print 'List of running processes:\n'
   for process in processes:
     print process.name
 
 
+def TestCaseSetup(args):
+  # Stop+start me2me host process.
+  if not RestartMe2MeHost():
+    # Host restart failed. Don't run any more tests.
+    raise Exception('Host restart failed.')
+
+  # Reset the user profile directory to start each test with a clean slate.
+  SetupUserProfileDir(args.me2me_manifest_file, args.it2me_manifest_file,
+                      args.user_profile_dir)
+
+
 def main(args):
 
   InitialiseTestMachineForLinux(args.cfg_file)
 
   with open(args.commands_file) as f:
     for line in f:
-      # Reset the user profile directory to start each test with a clean slate.
-      SetupUserProfileDir(args.me2me_manifest_file, args.it2me_manifest_file,
-                          args.user_profile_dir)
-
       # Replace the PROD_DIR value in the command-line with
       # the passed in value.
       line = line.replace(PROD_DIR_ID, args.prod_dir)
       # Launch specified command line for test.
-      LaunchBTCommand(line)
-      # After each test, stop+start me2me host process.
-      if not RestartMe2MeHost():
-        # Host restart failed. Don't run any more tests.
-        raise Exception('Host restart failed.')
-
-      # Print list of currently running processes.
-      PrintRunningProcesses()
+      LaunchBTCommand(args, line)
 
   # All tests completed. Include host-logs in the test results.
   host_log_contents = ''
   # There should be only 1 log file, as we delete logs on test completion.
   # Loop through matching files, just in case there are more.
   for log_file in glob.glob('/tmp/chrome_remote_desktop_*'):
     with open(log_file, 'r') as log:
       host_log_contents += '\nHOST LOG %s\n CONTENTS:\n%s' % (
           log_file, log.read())
   print host_log_contents
@@ skipping 20 matching lines @@
                       help='path to it2me host manifest file.')
   parser.add_argument(
       '-u', '--user_profile_dir',
       help='path to user-profile-dir, used by connect-to-host tests.')
   command_line_args = parser.parse_args()
   try:
     main(command_line_args)
   finally:
     # Stop host and cleanup user-profile-dir.
     TestMachineCleanup(command_line_args.user_profile_dir)