Add presubmit for gn formatting

PRESUBMIT.py

 # Copyright (c) 2012 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.
 
 """Top-level presubmit script for Chromium.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
 for more details about the presubmit API built into gcl.
 """
 
@@ skipping 1524 matching lines @@
             ('%s:%d uses mojo:// url format. Please use mojo: instead.')
              % (f.LocalPath(), lnum)))
   return errors
 
 
 def CheckChangeOnUpload(input_api, output_api):
   results = []
   results.extend(_CommonChecks(input_api, output_api))
   results.extend(_CheckValidHostsInDEPS(input_api, output_api))
   results.extend(_CheckJavaStyle(input_api, output_api))
+  results.extend(
+      input_api.canned_checks.CheckGNFormatted(input_api, output_api))
   return results
 
 
 def GetDefaultTryConfigs(bots=None):
   """Returns a list of ('bot', set(['tests']), optionally filtered by [bots].
 
   If 'bots' is specified, will only return configurations for bots in that list.
   """
 
   builders_and_tests = {
@@ skipping 40 matching lines @@
   builders = [
       'Mojo Linux Try',
       'Mojo Linux (dbg) Try',
       'Mojo Android Builder Try',
       'Mojo Android Builder (dbg) Try',
       'Mojo ChromeOS Builder Try',
       'Mojo ChromeOS Builder (dbg) Try',
   ]
 
   return GetDefaultTryConfigs(builders)