Ensure host_forwarder is killed when setting up/tearing down sharding.

build/android/pylib/base_test_sharder.py

 # 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.
 
 
 import android_commands
 import logging
 import multiprocessing
 
 from android_commands import errors
@@ skipping 48 matching lines @@
       device: Device serial where this shard will run
       index: Index of this device in the pool.
 
     Returns:
       An object of BaseTestRunner type (that can provide a "Run()" method).
     """
     pass
 
   def SetupSharding(self, tests):
     """Called before starting the shards."""
-    Forwarder.KillHost(self.build_type)
+    pass
 
   def OnTestsCompleted(self, test_runners, test_results):
     """Notifies that we completed the tests."""
+    pass
+
+  def _KillHostForwarder(self):
     Forwarder.KillHost(self.build_type)
 
   def RunShardedTests(self):
     """Runs the tests in all connected devices.
 
     Returns:
       A TestResults object.
     """
     logging.warning('*' * 80)
     logging.warning('Sharding in ' + str(len(self.attached_devices)) +
                     ' devices.')
     logging.warning('Note that the output is not synchronized.')
     logging.warning('Look for the "Final result" banner in the end.')
     logging.warning('*' * 80)
     final_results = TestResults()
+    self._KillHostForwarder()
     for retry in xrange(self.retries):
       logging.warning('Try %d of %d', retry + 1, self.retries)
       self.SetupSharding(self.tests)
       test_runners = []
 
       # Try to create N shards, and retrying on failure.
       try:
         for index, device in enumerate(self.attached_devices):
           logging.warning('*' * 80)
           logging.warning('Creating shard %d for %s', index, device)
@@ skipping 37 matching lines @@
         self.tests = []
         for t in test_results.GetAllBroken():
           self.tests += [t.name]
         if not self.tests:
           break
     else:
       # We ran out retries, possibly out of healthy devices.
       # There's no recovery at this point.
       raise Exception('Unrecoverable error while retrying test runs.')
     self.OnTestsCompleted(test_runners, final_results)
+    self._KillHostForwarder()
     return final_results