Rolling forward clang, hiding some warnings

tools/clang/blink_gc_plugin/tests/test.py

 #!/usr/bin/env python
 # 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 argparse
 import glob
 import os
 import subprocess
@@ skipping 45 matching lines @@
   result_file = '%s.txt%s' % (
       test_base_name, '' if reset_results else '.actual')
   try:
     expected = open('%s.txt' % test_base_name).read()
   except IOError:
     open(result_file, 'w').write(actual)
     return 'no expected file found'
 
   if expected != actual:
     open(result_file, 'w').write(actual)
-    return 'expected and actual differed'
+    error = 'expected and actual differed\n'
+    error += 'Actual:\n' + actual
+    error += 'Expected:\n' + expected
+    return error
 
 
 def run_tests(clang_path, plugin_path, reset_results):
   """Runs the tests.
 
   Args:
     clang_path: The path to the clang binary to be tested.
     plugin_path: An optional path to the plugin to test. This may be None, if
                  plugin is built directly into clang, like on Windows.
     reset_results: True if the results should be overwritten in place.
@@ skipping 57 matching lines @@
                                args.reset_results)
   print 'Ran %d tests: %d succeeded, %d failed' % (
       len(passing) + len(failing), len(passing), len(failing))
   for test in failing:
     print '    %s' % test
   return len(failing)
 
 
 if __name__ == '__main__':
   sys.exit(main())