Android gtest runner: Only query device for test list when necessary

build/android/pylib/gtest/gtest_test_instance.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 logging
 import os
 import re
 import sys
 import tempfile
 
@@ skipping 179 matching lines @@
       self._app_data_files = args.app_data_files
       if args.app_data_file_dir:
         self._app_data_file_dir = args.app_data_file_dir
       else:
         self._app_data_file_dir = tempfile.mkdtemp()
         logging.critical('Saving app files to %s', self._app_data_file_dir)
     else:
       self._app_data_files = None
       self._app_data_file_dir = None
 
+  @property
+  def gtest_filter(self):
+    return self._gtest_filter
+
   #override
   def TestType(self):
     return 'gtest'
 
   #override
   def SetUp(self):
     """Map data dependencies via isolate."""
     if self._isolate_delegate:
       self._isolate_delegate.Remap(
           self._isolate_abs_path, self._isolated_abs_path)
@@ skipping 140 matching lines @@
     return self._apk_helper and self._apk_helper.GetInstrumentationName()
 
   @property
   def shard_timeout(self):
     return self._shard_timeout
 
   @property
   def suite(self):
     return self._suite