DoomPartialEntry should not attempt to doom an already doomed entry.

net/http/http_cache.h

 // 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.
 
 // This file declares a HttpTransactionFactory implementation that can be
 // layered on top of another HttpTransactionFactory to add HTTP caching.  The
 // caching logic follows RFC 7234 (any exceptions are called out in the code).
 //
 // The HttpCache takes a disk_cache::Backend as a parameter, and uses that for
 // the cache storage.
@@ skipping 323 matching lines @@
 
   // Generates the cache key for this request.
   std::string GenerateCacheKey(const HttpRequestInfo*);
 
   // Dooms the entry selected by |key|, if it is currently in the list of active
   // entries.
   void DoomActiveEntry(const std::string& key);
 
   // Dooms the entry selected by |key|. |trans| will be notified via its IO
   // callback if this method returns ERR_IO_PENDING. The entry can be
-  // currently in use or not.
+  // currently in use or not. If entry is in use and the invoking transaction
+  // is associated with this entry and this entry is already doomed, this API
+  // should not be invoked.
   int DoomEntry(const std::string& key, Transaction* trans);
 
   // Dooms the entry selected by |key|. |trans| will be notified via its IO
   // callback if this method returns ERR_IO_PENDING. The entry should not
   // be currently in use.
   int AsyncDoomEntry(const std::string& key, Transaction* trans);
 
   // Dooms the entry associated with a GET for a given |url|.
   void DoomMainEntryForUrl(const GURL& url);
 
@@ skipping 195 matching lines @@
   THREAD_CHECKER(thread_checker_);
 
   base::WeakPtrFactory<HttpCache> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(HttpCache);
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_CACHE_H_