Add tool to reformat testing/buildbot/ json files in their canonical format.

testing/buildbot/PRESUBMIT.py

Index: testing/buildbot/PRESUBMIT.py
diff --git a/testing/PRESUBMIT.py b/testing/buildbot/PRESUBMIT.py
similarity index 70%
copy from testing/PRESUBMIT.py
copy to testing/buildbot/PRESUBMIT.py
index 5e8fc90625635e825a37dd1cb5faabf546e31fe7..a74562a656dc81dfa03724f4a7d6944be687856a 100644
--- a/testing/PRESUBMIT.py
+++ b/testing/buildbot/PRESUBMIT.py
@@ -2,7 +2,7 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-"""Top-level presubmit script for testing.
+"""Enforces json format.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
 for more details on the presubmit API built into depot_tools.
@@ -10,11 +10,10 @@ for more details on the presubmit API built into depot_tools.
 
 
 def CommonChecks(input_api, output_api):
-  output = []
-  blacklist = [r'gmock.*', r'gtest.*']
-  output.extend(input_api.canned_checks.RunPylint(
-      input_api, output_api, black_list=blacklist))
-  return output
+  args = [input_api.python_executable, 'manage.py', '--check']
+  cmd = input_api.Command(
+      name='manage', cmd=args, kwargs={}, message=output_api.PresubmitError)
+  return input_api.RunTests([cmd])
 
 
 def CheckChangeOnUpload(input_api, output_api):