Reland r212020: Move Python setup/tear down logic into Forwarder ...

build/android/bb_run_sharded_steps.py

 #!/usr/bin/env 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.
 
 """Helper script to shard build bot steps and save results to disk.
 
 Our buildbot infrastructure requires each slave to run steps serially.
 This is sub-optimal for android, where these steps can run independently on
@@ skipping 147 matching lines @@
   with file(steps, 'r') as f:
     steps = json.load(f)
   ret = 0
   for step_name in steps.keys():
     ret |= _PrintStepOutput(step_name)
   return ret
 
 
 def _KillPendingServers():
   for retry in range(5):
-    forwarder.Forwarder.KillHost()
     for server in ['lighttpd', 'web-page-replay']:
       pids = cmd_helper.GetCmdOutput(['pgrep', '-f', server])
       pids = [pid.strip() for pid in pids.split('\n') if pid.strip()]
       for pid in pids:
         try:
           logging.warning('Killing %s %s', server, pid)
           os.kill(int(pid), signal.SIGQUIT)
         except Exception as e:
           logging.warning('Failed killing %s %s %s', server, pid, e)
 
@@ skipping 15 matching lines @@
   options, urls = parser.parse_args(argv)
   if options.print_results:
     return _PrintStepOutput(options.print_results)
   if options.print_all:
     return _PrintAllStepsOutput(options.print_all)
 
   # At this point, we should kill everything that may have been left over from
   # previous runs.
   _KillPendingServers()
 
+  forwarder.Forwarder.UseMultiprocessing()
+
   # Reset the test port allocation. It's important to do it before starting
   # to dispatch any step.
   if not ports.ResetTestServerPortAllocation():
     raise Exception('Failed to reset test server port.')
 
   # Sort the devices so that we'll try to always run a step in the same device.
   devices = sorted(android_commands.GetAttachedDevices())
   if not devices:
     print 'You must attach a device'
     return 1
 
   with file(options.steps, 'r') as f:
     steps = json.load(f)
   flaky_steps = []
   if options.flaky_steps:
     with file(options.flaky_steps, 'r') as f:
       flaky_steps = json.load(f)
   return _RunShardedSteps(steps, flaky_steps, devices)
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv))