[tools/perf] Improve the regex to find the commited revision

tools/perf/diagnose_test_failure

 #!/usr/bin/env python
 # 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 argparse
 import re
 import sys
 import urllib2
 
 
 _BUILD_REGEX = r'builds/(\d+)'
-_REVISION_REGEX = r'Cr-Commit-Position: refs/heads/master@{#(\d+)}'
+_REVISION_REGEX = r'\nCr-Commit-Position: refs/heads/master@{#(\d+)}'
 
 
 class _Color(object):
     HEADER = '\033[95m'
     OKBLUE = '\033[94m'
     OKGREEN = '\033[92m'
     WARNING = '\033[93m'
     FAIL = '\033[91m'
     ENDC = '\033[0m'
     BOLD = '\033[1m'
@@ skipping 72 matching lines @@
           (min(first_failure_revisions), max(first_failure_revisions)),
           len(set(first_failure_revisions))),
       _Color.BOLD, _Color.OKGREEN)
   _PrintWithColor('First failed build: %s' % first_failed_build,
                   _Color.BOLD, _Color.OKGREEN)
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(Main(sys.argv[1:]))