Let prefetched resources skip cache revalidation once for a short duration.

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 2616 (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 19 matching lines @@
 #include "net/base/completion_callback.h"
 #include "net/base/load_states.h"
 #include "net/base/net_export.h"
 #include "net/base/request_priority.h"
 #include "net/http/http_network_session.h"
 #include "net/http/http_transaction_factory.h"
 
 class GURL;
 
 namespace base {
+class Clock;
 class SingleThreadTaskRunner;
 }  // namespace base
 
 namespace disk_cache {
 class Backend;
 class Entry;
 }  // namespace disk_cache
 
 namespace net {
 
 class CertVerifier;
 class ChannelIDService;
 class DiskBasedCertCache;
 class HostResolver;
 class HttpAuthHandlerFactory;
+class HttpCachePrefetchValidationTest;
 class HttpNetworkSession;
 class HttpResponseInfo;
 class HttpServerProperties;
 class IOBuffer;
 class NetLog;
 class NetworkDelegate;
 class ProxyService;
 class SSLConfigService;
 class TransportSecurityState;
 class ViewCacheHelper;
@@ skipping 175 matching lines @@
     // Must remain at the end of the enum.
     kNumCacheEntryDataIndices
   };
 
   class MetadataWriter;
   class QuicServerInfoFactoryAdaptor;
   class Transaction;
   class WorkItem;
   friend class Transaction;
   friend class ViewCacheHelper;
+  friend class HttpCachePrefetchValidationTest;
   struct PendingOp;  // Info for an entry under construction.
   class AsyncValidation;  // Encapsulates a single async revalidation.
 
   typedef std::list<Transaction*> TransactionList;
   typedef std::list<WorkItem*> WorkItemList;
   typedef std::map<std::string, AsyncValidation*> AsyncValidationMap;
 
   struct ActiveEntry {
     explicit ActiveEntry(disk_cache::Entry* entry);
     ~ActiveEntry();
 
     disk_cache::Entry* disk_entry;
     Transaction*       writer;
     TransactionList    readers;
     TransactionList    pending_queue;
     bool               will_process_pending_queue;
     bool               doomed;
   };
 
   typedef base::hash_map<std::string, ActiveEntry*> ActiveEntriesMap;
   typedef base::hash_map<std::string, PendingOp*> PendingOpsMap;
   typedef std::set<ActiveEntry*> ActiveEntriesSet;
   typedef base::hash_map<std::string, int> PlaybackCacheMap;
 
+  // The number of minutes after a resource is prefetched that it can be used
+  // again without validation.
+  static const int kPrefetchReuseMins = 5;
+
   // Methods ------------------------------------------------------------------
 
   // Creates the |backend| object and notifies the |callback| when the operation
   // completes. Returns an error code.
   int CreateBackend(disk_cache::Backend** backend,
                     const net::CompletionCallback& callback);
 
   // Makes sure that the backend creation is complete before allowing the
   // provided transaction to use the object. Returns an error code.  |trans|
   // will be notified via its IO callback if this method returns ERR_IO_PENDING.
@@ skipping 164 matching lines @@
   ActiveEntriesSet doomed_entries_;
 
   // The set of entries "under construction".
   PendingOpsMap pending_ops_;
 
   scoped_ptr<PlaybackCacheMap> playback_cache_map_;
 
   // The async validations currently in progress, keyed by URL.
   AsyncValidationMap async_validations_;
 
+  // A clock that can be swapped out for testing.
+  scoped_ptr<base::Clock> clock_;
+
   base::WeakPtrFactory<HttpCache> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(HttpCache);
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_CACHE_H_