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

build/android/pylib/gtest/gtest_test_instance.py

Index: build/android/pylib/gtest/gtest_test_instance.py
diff --git a/build/android/pylib/gtest/gtest_test_instance.py b/build/android/pylib/gtest/gtest_test_instance.py
index c32adb282a3ac6a600df272b079fdcf7e558a31f..e61b89c8fa0c3d89975df402a0254de3a668a23b 100644
--- a/build/android/pylib/gtest/gtest_test_instance.py
+++ b/build/android/pylib/gtest/gtest_test_instance.py
@@ -197,6 +197,10 @@ class GtestTestInstance(test_instance.TestInstance):
       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'