Make SimpleEntryImpl::Doom() completely asynchronous.

net/disk_cache/simple/simple_entry_impl.h

 // Copyright (c) 2013 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_DISK_CACHE_SIMPLE_SIMPLE_ENTRY_IMPL_H_
 #define NET_DISK_CACHE_SIMPLE_SIMPLE_ENTRY_IMPL_H_
 
 #include <string>
 
 #include "base/file_path.h"
@@ skipping 95 matching lines @@
   // |last_used_|, |last_modified_| and |data_size_| are copied from the
   // synchronous entry at the completion of each item of asynchronous IO.
   base::Time last_used_;
   base::Time last_modified_;
   int32 data_size_[kSimpleEntryFileCount];
 
   // The |synchronous_entry_| is the worker thread object that performs IO on
   // entries. It is set to NULL while operations are pending to prevent unsafe
   // access from multiple threads.
   SimpleSynchronousEntry* synchronous_entry_;
-
-  bool has_been_doomed_;
 };
 
 }  // namespace disk_cache
 
 #endif  // NET_DISK_CACHE_SIMPLE_SIMPLE_ENTRY_IMPL_H_