Do not leak when iterator outlives disk cache backend.

net/disk_cache/blockfile/backend_impl.h

Index: net/disk_cache/blockfile/backend_impl.h
diff --git a/net/disk_cache/blockfile/backend_impl.h b/net/disk_cache/blockfile/backend_impl.h
index 775374e2c3bcbf39f347e4dc1a68a938274b6087..1abc66dae8e84703b039bc8b94d5e3bb7c0876a6 100644
--- a/net/disk_cache/blockfile/backend_impl.h
+++ b/net/disk_cache/blockfile/backend_impl.h
@@ -74,14 +74,14 @@ class NET_EXPORT_PRIVATE BackendImpl : public Backend {
   int SyncDoomEntriesBetween(base::Time initial_time,
                              base::Time end_time);
   int SyncDoomEntriesSince(base::Time initial_time);
-  int SyncOpenNextEntry(void** iter, Entry** next_entry);
-  void SyncEndEnumeration(void* iter);
+  int SyncOpenNextEntry(Rankings::Iterator* iterator, Entry** next_entry);
+  void SyncEndEnumeration(scoped_ptr<Rankings::Iterator> iterator);
   void SyncOnExternalCacheHit(const std::string& key);
 
   // Open or create an entry for the given |key| or |iter|.
   EntryImpl* OpenEntryImpl(const std::string& key);
   EntryImpl* CreateEntryImpl(const std::string& key);
-  EntryImpl* OpenNextEntryImpl(void** iter);
+  EntryImpl* OpenNextEntryImpl(Rankings::Iterator* iter);
 
   // Sets the maximum size for the total amount of data stored by this instance.
   bool SetMaxSize(int max_bytes);