Removing AccessLog class. This is a partial revert of yzshen's r74872.

net/url_request/url_request_throttler_manager.h

 // Copyright (c) 2010 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.
 
 #ifndef NET_URL_REQUEST_URL_REQUEST_THROTTLER_MANAGER_H_
 #define NET_URL_REQUEST_URL_REQUEST_THROTTLER_MANAGER_H_
 
 #include <map>
 #include <string>
 
@@ skipping 84 matching lines @@
   // This keeps track of how many requests have been made. Used with
   // GarbageCollectEntries.
   unsigned int requests_since_last_gc_;
 
   mutable scoped_ptr<GURL::Replacements> url_id_replacements_;
 
   // Whether we would like to reject outgoing HTTP requests during the back-off
   // period.
   bool enforce_throttling_;
 
-  // Whether to record threads that have accessed the URLRequestThrottlerManager
-  // singleton object.
-  // TODO(yzshen): It is used for diagnostic purpose and should be removed once
-  // we figure out crbug.com/71721
-  bool record_access_log_;
-
   DISALLOW_COPY_AND_ASSIGN(URLRequestThrottlerManager);
 };
 
 }  // namespace net
 
 #endif  // NET_URL_REQUEST_URL_REQUEST_THROTTLER_MANAGER_H_