Remove void** from disk_cache interface.

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 e2304ffdcd1339e1a493161b5e502c437f7d9937..6c8239c2cc4172c529cfb96530c4add6485034f1 100644
--- a/net/disk_cache/blockfile/backend_impl.h
+++ b/net/disk_cache/blockfile/backend_impl.h
@@ -273,9 +273,15 @@ class NET_EXPORT_PRIVATE BackendImpl : public Backend {
                                  const CompletionCallback& callback) OVERRIDE;
   virtual int DoomEntriesSince(base::Time initial_time,
                                const CompletionCallback& callback) OVERRIDE;
-  virtual int OpenNextEntry(void** iter, Entry** next_entry,
-                            const CompletionCallback& callback) OVERRIDE;
-  virtual void EndEnumeration(void** iter) OVERRIDE;
+  // NOTE: The blockfile Backend::Iterator::OpenNextEntry method does not modify
+  // the last_used field of the entry, and therefore it does not impact the
+  // eviction ranking of the entry. However, an enumeration will go through all
+  // entries on the cache only if the cache is not modified while the
+  // enumeration is taking place. Significantly altering the entry pointed by
+  // the iterator (for example, deleting the entry) will invalidate the
+  // iterator. Performing operations on an entry that modify the entry may
+  // result in loops in the iteration, skipped entries or similar.
+  virtual scoped_ptr<Iterator> CreateIterator() OVERRIDE;
   virtual void GetStats(StatsItems* stats) OVERRIDE;
   virtual void OnExternalCacheHit(const std::string& key) OVERRIDE;