Public API changes are allowed if an owner is TBR'ed

PRESUBMIT.py

 # Copyright (c) 2013 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 Skia.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
 for more details about the presubmit API built into gcl.
 """
 
 import fnmatch
 import os
 import re
 import sys
 import traceback
 
 
 REVERT_CL_SUBJECT_PREFIX = 'Revert '
 
 SKIA_TREE_STATUS_URL = 'http://skia-tree-status.appspot.com'
 
+# Please add the complete email address here (and not just 'xyz@' or 'xyz').
 PUBLIC_API_OWNERS = (
     'reed@chromium.org',
     'reed@google.com',
     'bsalomon@chromium.org',
     'bsalomon@google.com',
     'djsollen@chromium.org',
     'djsollen@google.com',
 )
 
 AUTHORS_FILE_NAME = 'AUTHORS'
@@ skipping 166 matching lines @@
     return results
 
   lgtm_from_owner = False
   issue = input_api.change.issue
   if issue and input_api.rietveld:
     issue_properties = input_api.rietveld.get_issue_properties(
         issue=int(issue), messages=True)
     if re.match(REVERT_CL_SUBJECT_PREFIX, issue_properties['subject'], re.I):
       # It is a revert CL, ignore the public api owners check.
       return results
+
+    match = re.search(r'^TBR=(.*)$', issue_properties['description'], re.M)
+    if match:
+      tbr_entries = match.group(1).strip().split(',')
+      for owner in PUBLIC_API_OWNERS:
+        if owner in tbr_entries or owner.split('@')[0] in tbr_entries:
+          # If an owner is specified in the TBR= line then ignore the public
+          # api owners check.
+          return results
+
     if issue_properties['owner_email'] in PUBLIC_API_OWNERS:
       # An owner created the CL that is an automatic LGTM.
       lgtm_from_owner = True
 
     messages = issue_properties.get('messages')
     if messages:
       for message in messages:
         if (message['sender'] in PUBLIC_API_OWNERS and
             'lgtm' in message['text'].lower()):
           # Found an lgtm in a message from an owner.
@@ skipping 18 matching lines @@
     state and an error if it is in 'Closed' state.
   """
   results = []
   results.extend(_CommonChecks(input_api, output_api))
   results.extend(
       _CheckTreeStatus(input_api, output_api, json_url=(
           SKIA_TREE_STATUS_URL + '/banner-status?format=json')))
   results.extend(_CheckLGTMsForPublicAPI(input_api, output_api))
   results.extend(_CheckOwnerIsInAuthorsFile(input_api, output_api))
   return results