Do not enforce the public API presubmit check for Revert CLs

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 os
+import re
 import sys
 
 
+REVERT_CL_SUBJECT_PREFIX = 'Revert '
+
 SKIA_TREE_STATUS_URL = 'http://skia-tree-status.appspot.com'
 
 PUBLIC_API_OWNERS = (
     'reed@chromium.org',
     'reed@google.com',
     'bsalomon@chromium.org',
     'bsalomon@google.com',
-    'rmistry@google.com',  # For emergency reverts only.
 )
 
 
 def _CheckChangeHasEol(input_api, output_api, source_file_filter=None):
   """Checks that files end with atleast one \n (LF)."""
   eof_files = []
   for f in input_api.AffectedSourceFiles(source_file_filter):
     contents = input_api.ReadFile(f, 'rb')
     # Check that the file ends in atleast one newline character.
     if len(contents) > 1 and contents[-1:] != '\n':
@@ skipping 86 matching lines @@
       requires_owner_check = True
 
   if not requires_owner_check:
     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
     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.
           lgtm_from_owner = True
           break;
-       
+
   if not lgtm_from_owner:
     results.append(
         output_api.PresubmitError(
             'Since the CL is editing public API, you must have an LGTM from '
             'one of: %s' % str(PUBLIC_API_OWNERS)))
   return results
 
 
 def CheckChangeOnCommit(input_api, output_api):
   """Presubmit checks for the change on commit.
 
   The following are the presubmit checks:
   * Check change has one and only one EOL.
   * Ensures that the Skia tree is open in
     http://skia-tree-status.appspot.com/. Shows a warning if it is in 'Caution'
     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))
   return results