Connect SimpleCache Backend active_entries_ more closely to Entry lifetime.

net/disk_cache/simple/simple_backend_impl.h

Index: net/disk_cache/simple/simple_backend_impl.h
diff --git a/net/disk_cache/simple/simple_backend_impl.h b/net/disk_cache/simple/simple_backend_impl.h
index f65f56611ff1e75a5e6a11b5d5b46703f1a03c81..2bd00818b9cfb1f550f432f9f53521b41b66f049 100644
--- a/net/disk_cache/simple/simple_backend_impl.h
+++ b/net/disk_cache/simple/simple_backend_impl.h
@@ -66,10 +66,6 @@ class NET_EXPORT_PRIVATE SimpleBackendImpl : public Backend,
   // Returns the maximum file size permitted in this backend.
   int GetMaxFileSize() const;
 
-  // Removes |entry| from the |active_entries_| set, forcing future Open/Create
-  // operations to construct a new object.
-  void OnDeactivated(const SimpleEntryImpl* entry);
-
   // Flush our SequencedWorkerPool.
   static void FlushWorkerPoolForTesting();
 
@@ -109,11 +105,14 @@ class NET_EXPORT_PRIVATE SimpleBackendImpl : public Backend,
   virtual void OnExternalCacheHit(const std::string& key) OVERRIDE;
 
  private:
-  typedef base::hash_map<uint64, base::WeakPtr<SimpleEntryImpl> > EntryMap;
+  typedef base::hash_map<uint64, SimpleEntryImpl*> EntryMap;
 
   typedef base::Callback<void(base::Time mtime, uint64 max_size, int result)>
       InitializeIndexCallback;
 
+  class ActiveEntryProxy;
+  friend class ActiveEntryProxy;
+
   // Return value of InitCacheStructureOnDisk().
   struct DiskStatResult {
     base::Time cache_dir_mtime;