Mojo: Add a utility to compare old mojom_bindings_generator.py output to the current one.

mojo/tools/test_runner.py

 #!/usr/bin/env python
 # 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.
 
 """A "smart" test runner for gtest unit tests (that caches successes)."""
 
 import logging
 import os
 import subprocess
 import sys
 
 _logging = logging.getLogger()
 
-_script_dir = os.path.dirname(os.path.realpath(__file__))
+_script_dir = os.path.dirname(os.path.abspath(__file__))
 sys.path.insert(0, os.path.join(_script_dir, "pylib"))
 
 from transitive_hash import transitive_hash
 
 def main(argv):
   logging.basicConfig()
   # Uncomment to debug:
   # _logging.setLevel(logging.DEBUG)
 
   if len(argv) < 3 or len(argv) > 4:
@@ skipping 73 matching lines @@
       print "  Failed to start test"
       return 1
   print "All tests succeeded"
   if successes_cache_file:
     successes_cache_file.close()
 
   return 0
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv))