Include Closure Compiler in CQ bots for ui/file_manager.

This adds:
  Q_INCLUDE_TRYBOTS=tryserver.chromium.linux:closure_compilation
to CLs in ui/file_manager.

BUG=none
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2357733003
Cr-Commit-Position: refs/heads/master@{#419986}

ui/file_manager/PRESUBMIT.py

+# Copyright 2016 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 re
+
+
+def PostUploadHook(cl, change, output_api):
+  rietveld_obj = cl.RpcServer()
+  description = rietveld_obj.get_description(cl.issue)
+
+  existing_bots = (change.CQ_INCLUDE_TRYBOTS or '').split(';')
+  clean_bots = set(filter(None, map(lambda s: s.strip(), existing_bots)))
+  new_bots = clean_bots | set(
+      ['master.tryserver.chromium.linux:closure_compilation'])
+  new_tag = 'CQ_INCLUDE_TRYBOTS=%s' % ';'.join(new_bots)
+
+  if clean_bots:
+    tag_reg = '^CQ_INCLUDE_TRYBOTS=.*$'
+    new_description = re.sub(tag_reg, new_tag, description, flags=re.M | re.I)
+  else:
+    new_description = description + '\n' + new_tag
+
+  if new_description == description:
+    return []
+
+  rietveld_obj.update_description(cl.issue, new_description)
+  return [output_api.PresubmitNotifyResult(
+      'Automatically added optional Closure bots to run on CQ.')]