Revert of Remove void** from disk_cache interface.

net/disk_cache/blockfile/backend_impl_v3.cc

Index: net/disk_cache/blockfile/backend_impl_v3.cc
diff --git a/net/disk_cache/blockfile/backend_impl_v3.cc b/net/disk_cache/blockfile/backend_impl_v3.cc
index b44b1950abc9205b0d67bd3ff55533d8f0543442..9a7cff1c79000c8e9e41f9f7728da3bf025cc680 100644
--- a/net/disk_cache/blockfile/backend_impl_v3.cc
+++ b/net/disk_cache/blockfile/backend_impl_v3.cc
@@ -660,27 +660,17 @@
   }
 }
 
-class BackendImplV3::IteratorImpl : public Backend::Iterator {
- public:
-  explicit IteratorImpl(base::WeakPtr<InFlightBackendIO> background_queue)
-      : background_queue_(background_queue), data_(NULL) {
-  }
-
-  virtual int OpenNextEntry(Entry** next_entry,
-                            const net::CompletionCallback& callback) OVERRIDE {
-    if (!background_queue_)
-      return net::ERR_FAILED;
-    background_queue_->OpenNextEntry(&data_, next_entry, callback);
-    return net::ERR_IO_PENDING;
-  }
-
- private:
-  const base::WeakPtr<InFlightBackendIO> background_queue_;
-  void* data_;
-};
-
-scoped_ptr<Backend::Iterator> BackendImplV3::CreateIterator() {
-  return scoped_ptr<Backend::Iterator>(new IteratorImpl(GetBackgroundQueue()));
+int BackendImplV3::OpenNextEntry(void** iter, Entry** next_entry,
+                                 const CompletionCallback& callback) {
+  DCHECK(!callback.is_null());
+  background_queue_.OpenNextEntry(iter, next_entry, callback);
+  return net::ERR_IO_PENDING;
+}
+
+void BackendImplV3::EndEnumeration(void** iter) {
+  scoped_ptr<IndexIterator> iterator(
+      reinterpret_cast<IndexIterator*>(*iter));
+  *iter = NULL;
 }
 
 void BackendImplV3::GetStats(StatsItems* stats) {
@@ -1507,17 +1497,13 @@
   return net::ERR_FAILED;
 }
 
-
-class BackendImplV3::NotImplementedIterator : public Backend::Iterator {
- public:
-  virtual int OpenNextEntry(disk_cache::Entry** next_entry,
-                            const net::CompletionCallback& callback) OVERRIDE {
-    return net::ERR_NOT_IMPLEMENTED;
-  }
-};
-
-scoped_ptr<Backend::Iterator> BackendImplV3::CreateIterator() {
-  return scoped_ptr<Iterator>(new NotImplementedIterator());
+int BackendImplV3::OpenNextEntry(void** iter, Entry** next_entry,
+                                 const CompletionCallback& callback) {
+  return net::ERR_FAILED;
+}
+
+void BackendImplV3::EndEnumeration(void** iter) {
+  NOTIMPLEMENTED();
 }
 
 void BackendImplV3::GetStats(StatsItems* stats) {