Add gcl presubmit script to the dart src tree.

Currently I just added a tree status check but we can extend this over time.
Review URL: https://chromiumcodereview.appspot.com//10891021

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@11575 260f80e4-7a28-3924-810f-c04153c831b5

Author: ricowind

PRESUBMIT.py

@@ -0,0 +1,18 @@
+# Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+# for details. 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 Dart.
+
+See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
+for more details about the presubmit API built into gcl.
+"""
+
+def CheckChangeOnCommit(input_api, output_api):
+  results = []
+  status_check = input_api.canned_checks.CheckTreeIsOpen(
+      input_api,
+      output_api,
+      json_url='http://dart-status.appspot.com/current?format=json')
+  results.extend(status_check)
+  return results