Making safely-roll-webkit.py work with "new git workflow"

tools/safely-roll-webkit.py

 #!/usr/bin/env python
-# Copyright (c) 2011 The Chromium Authors. All rights reserved.
+# Copyright (c) 2012 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.
 
 """Generate a CL to roll webkit to the specified revision number and post
 it to Rietveld so that the CL will land automatically if it passes the
 commit-queue's checks.
 """
 
 import logging
 import optparse
@@ skipping 45 matching lines @@
   print msg
 
   # Silence the editor.
   os.environ['EDITOR'] = 'true'
 
   old_branch = scm.GIT.GetBranch(root_dir)
   if old_branch == 'webkit_roll':
     parser.error(
         'Please delete the branch webkit_roll and move to a different branch')
   subprocess2.check_output(
-      ['git', 'checkout', '-b', 'webkit_roll', 'origin/trunk'])
+      ['git', 'checkout', '-b', 'webkit_roll', 'origin/master'])
   try:
     process_deps(os.path.join(root_dir, 'DEPS'), new_rev)
     commit_msg = msg + '\n\nTBR=\n'
     subprocess2.check_output(['git', 'commit', '-m', commit_msg, 'DEPS'])
-    subprocess2.check_call(['git', 'diff', 'origin/trunk'])
+    subprocess2.check_call(['git', 'diff', 'origin/master'])
     subprocess2.check_call(['git', 'cl', 'upload', '--use-commit-queue'])
   finally:
     subprocess2.check_output(['git', 'checkout', old_branch])
     subprocess2.check_output(['git', 'branch', '-D', 'webkit_roll'])
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main())