[android] Clean up a couple of unnecessary test runner log warnings.

build/android/pylib/instrumentation/instrumentation_test_instance.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 collections
 import copy
 import json
 import logging
 import os
 import pickle
@@ skipping 667 matching lines @@
   def _initializeTestCoverageAttributes(self, args):
     self._coverage_directory = args.coverage_dir
 
   def _initializeTombstonesAttributes(self, args):
     self._store_tombstones = args.store_tombstones
 
   def _initializeLogAttributes(self, args):
     self._should_save_logcat = bool(args.json_results_file)
 
   def _initializeEditPrefsAttributes(self, args):
-    if not hasattr(args, 'shared_prefs_file'):
+    if not hasattr(args, 'shared_prefs_file') or not args.shared_prefs_file:
       return
     if not isinstance(args.shared_prefs_file, str):
       logging.warning("Given non-string for a filepath")
       return
 
     # json.load() loads strings as unicode, which causes issues when trying
     # to edit string values in preference files, so convert to Python strings
     def unicode_to_str(data):
       if isinstance(data, dict):
         return {unicode_to_str(key): unicode_to_str(value)
@@ skipping 183 matching lines @@
 
   @staticmethod
   def GenerateTestResults(
       result_code, result_bundle, statuses, start_ms, duration_ms):
     return GenerateTestResults(result_code, result_bundle, statuses,
                                start_ms, duration_ms)
 
   #override
   def TearDown(self):
     pass