Add support for Junit tests in platform mode.

build/android/pylib/base/test_run.py

 # Copyright 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.
 
 
 class TestRun(object):
   """An execution of a particular test on a particular device.
 
   This is expected to handle all logic that is specific to the combination of
   environment and test type.
 
   Examples include:
     - local gtests
     - local instrumentation tests
   """
 
   def __init__(self, env, test_instance):
     self._env = env
     self._test_instance = test_instance
 
   def TestPackage(self):
     raise NotImplementedError
 
   def SetUp(self):
     raise NotImplementedError
 
   def RunTests(self):
+    """Runs Tests and returns test results.
+
+    Returns:
+      Should return list of |base_test_result.TestRunResults| objects.
+    """
     raise NotImplementedError
 
   def TearDown(self):
     raise NotImplementedError
 
   def __enter__(self):
     self.SetUp()
     return self
 
   def __exit__(self, exc_type, exc_val, exc_tb):
     self.TearDown()