[Android] Implement perf tests to platform mode.

build/android/pylib/local/device/local_device_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.
 
 import fnmatch
 import functools
 import imp
 import logging
 import signal
 import thread
@@ skipping 182 matching lines @@
     return test
 
   def _GetTests(self):
     raise NotImplementedError
 
   def _RunTest(self, device, test):
     raise NotImplementedError
 
   def _ShouldShard(self):
     raise NotImplementedError
+
+
+class NoTestsError(Exception):
+  """Error for when no tests are found."""