Rewrite presubmit scripts to use new EnsureCQIncludeTrybotsAreAdded.

ui/webui/resources/PRESUBMIT.py

Index: ui/webui/resources/PRESUBMIT.py
diff --git a/ui/webui/resources/PRESUBMIT.py b/ui/webui/resources/PRESUBMIT.py
index 7a7e28be99ddb44575f9a16422b525cb74d42cf6..7f7d1d91aa6775cb816af0e805aa20b14c9d11de 100644
--- a/ui/webui/resources/PRESUBMIT.py
+++ b/ui/webui/resources/PRESUBMIT.py
@@ -6,27 +6,12 @@ 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.')]
+  return output_api.EnsureCQIncludeTrybotsAreAdded(
+    cl,
+    [
+      'master.tryserver.chromium.linux:closure_compilation',
+    ],
+    'Automatically added optional Closure bots to run on CQ.')
 
 
 def CheckChangeOnUpload(input_api, output_api):