[webpagereplay] Add command exit.

customhandlers.py

 #!/usr/bin/env python
 # Copyright 2010 Google Inc. All Rights Reserved.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
 #
 #      http://www.apache.org/licenses/LICENSE-2.0
 #
 # Unless required by applicable law or agreed to in writing, software
@@ skipping 173 matching lines @@
       return SimpleResponse(200)
     elif command == 'status':
       status = {}
       is_record_mode = self.server_manager.IsRecordMode()
       status['is_record_mode'] = is_record_mode
       status['options'] = json.loads(str(self.options))
       archive_stats = self.http_archive.stats()
       if archive_stats:
         status['archive_stats'] = json.loads(archive_stats)
       return JsonResponse(status)
+    elif command == 'exit':
+      self.server_manager.should_exit = True
+      return SimpleResponse(200)
     return None