Don't maintain a second level of timeouts.

net/ssl/ssl_client_session_cache.h

 // Copyright 2015 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_SSL_SSL_CLIENT_SESSION_CACHE_H
 #define NET_SSL_SSL_CLIENT_SESSION_CACHE_H
 
 #include <stddef.h>
+#include <time.h>
 
 #include <memory>
 #include <string>
 
 #include "base/bind.h"
 #include "base/containers/mru_cache.h"
 #include "base/macros.h"
 #include "base/memory/memory_coordinator_client.h"
 #include "base/memory/memory_pressure_monitor.h"
 #include "base/synchronization/lock.h"
 #include "base/threading/thread_checker.h"
 #include "base/time/time.h"
 #include "net/base/net_export.h"
 #include "third_party/boringssl/src/include/openssl/base.h"
 
 namespace base {
 class Clock;
 }
 
 namespace net {
 
 class NET_EXPORT SSLClientSessionCache : public base::MemoryCoordinatorClient {
  public:
   struct Config {
     // The maximum number of entries in the cache.
     size_t max_entries = 1024;
     // The number of calls to Lookup before a new check for expired sessions.
     size_t expiration_check_count = 256;
-    // How long each session should last.
-    base::TimeDelta timeout = base::TimeDelta::FromHours(1);
   };
 
   explicit SSLClientSessionCache(const Config& config);
   ~SSLClientSessionCache() override;
 
   size_t size() const;
 
   // Returns the session associated with |cache_key| and moves it to the front
   // of the MRU list. Returns nullptr if there is none.
   bssl::UniquePtr<SSL_SESSION> Lookup(const std::string& cache_key);
 
   // Inserts |session| into the cache at |cache_key|. If there is an existing
   // one, it is released. Every |expiration_check_count| calls, the cache is
   // checked for stale entries.
   void Insert(const std::string& cache_key, SSL_SESSION* session);
 
   // Removes all entries from the cache.
   void Flush();
 
   void SetClockForTesting(std::unique_ptr<base::Clock> clock);
 
  private:
-  struct CacheEntry {
-    CacheEntry();
-    ~CacheEntry();
-
-    bssl::UniquePtr<SSL_SESSION> session;
-    // The time at which this entry was created.
-    base::Time creation_time;
-  };
-
-  using CacheEntryMap =
-      base::HashingMRUCache<std::string, std::unique_ptr<CacheEntry>>;
-
   // base::MemoryCoordinatorClient implementation:
   void OnMemoryStateChange(base::MemoryState state) override;
 
   // Returns true if |entry| is expired as of |now|.
-  bool IsExpired(CacheEntry* entry, const base::Time& now);
+  bool IsExpired(SSL_SESSION* session, time_t now);
 
   // Removes all expired sessions from the cache.
   void FlushExpiredSessions();
 
   // Clear cache on low memory notifications callback.
   void OnMemoryPressure(
       base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level);
 
   std::unique_ptr<base::Clock> clock_;
   Config config_;
-  CacheEntryMap cache_;
+  base::HashingMRUCache<std::string, bssl::UniquePtr<SSL_SESSION>> cache_;
   size_t lookups_since_flush_;
 
   // TODO(davidben): After https://crbug.com/458365 is fixed, replace this with
   // a ThreadChecker. The session cache should be single-threaded like other
   // classes in net.
   base::Lock lock_;
 
   std::unique_ptr<base::MemoryPressureListener> memory_pressure_listener_;
 
   DISALLOW_COPY_AND_ASSIGN(SSLClientSessionCache);
 };
 
 }  // namespace net
 
 #endif  // NET_SSL_SSL_CLIENT_SESSION_CACHE_H