When reverting, just reverse merge the entire revision.

drover.py

 #!/usr/bin/env python
 # 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.
 
 import collections
 import datetime
 import json
 import optparse
 import os
@@ skipping 257 matching lines @@
   paths = getBestExportPathsMap(url, revision).keys()
   paths.sort()
   paths.reverse()
 
   for path in paths:
     command = "svn delete ." + path
     print command
     os.system(command)
 
 def revertRevision(url, revision):
-  paths = getBestMergePaths(url, revision)
-  for path in paths:
-    command = ('svn merge -N -r ' + str(revision) + ":" + str(revision-1) +
-                " " + url + path + " ." + path)
-    print command
-    os.system(command)
+  command = ('svn merge --ignore-ancestry -c -%d %s .' % (revision, url))
+  print command
+  os.system(command)
 
 def getFileInfo(url, revision):
   global files_info_
 
   if (files_info_ != None):
     return files_info_
 
   svn_log = subprocess2.check_output(
       ['svn', 'log', url, '-r', str(revision), '-v']).splitlines()
 
@@ skipping 414 matching lines @@
 
   if options.branch and options.milestone:
     option_parser.error("--branch cannot be used with --milestone")
     return 1
 
   return drover(options, args)
 
 
 if __name__ == "__main__":
   sys.exit(main())