[Android] Add support for external sharding to the test runner.

build/android/pylib/local/device/local_device_instrumentation_test_run.py

 # Copyright 2015 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
 import os
 import posixpath
 import re
 import time
 
@@ skipping 187 matching lines @@
     if not str(device) in self._flag_changers:
       self._flag_changers[str(device)] = flag_changer.FlagChanger(
         device, self._test_instance.package_info.cmdline_file)
 
   #override
   def _CreateShards(self, tests):
     return tests
 
   #override
   def _GetTests(self):
-    return self._test_instance.GetTests()
+    tests = self._test_instance.GetTests()
+    tests = self._ApplyExternalSharding(
+        tests, self._test_instance.external_shard_index,
+        self._test_instance.total_external_shards)
+    return tests
 
   #override
   def _GetUniqueTestName(self, test):
     return instrumentation_test_instance.GetUniqueTestName(test)
 
   #override
   def _RunTest(self, device, test):
     extras = {}
 
     flags = None
@@ skipping 206 matching lines @@
         timeout = v
         break
     else:
       logging.warning('Using default 1 minute timeout for %s', test_name)
       timeout = 60
 
     timeout *= cls._GetTimeoutScaleFromAnnotations(annotations)
 
     return timeout