DOMStorageContextImpl that's implemented in terms of the new dom_storage classes.

content/browser/renderer_host/render_message_filter.cc

Index: content/browser/renderer_host/render_message_filter.cc
===================================================================
--- content/browser/renderer_host/render_message_filter.cc	(revision 127221)
+++ content/browser/renderer_host/render_message_filter.cc	(working copy)
@@ -411,9 +411,21 @@
     return;
   }
 
+#ifdef ENABLE_NEW_DOM_STORAGE_BACKEND
+  // TODO(michaeln): Fix this.
+  // This is a bug in the existing impl, session storage is effectively
+  // leaked when created thru this code path (window.open()) since there
+  // is no balancing DeleteSessionStorage() for this Clone() call anywhere
+  // in the codebase. I'm replicating the bug for now.
   *cloned_session_storage_namespace_id =
+      dom_storage_context_->LeakyCloneSessionStorage(
+          params.session_storage_namespace_id);
+#else
+  *cloned_session_storage_namespace_id =
       dom_storage_context_->CloneSessionStorage(
           params.session_storage_namespace_id);
+#endif
+
   render_widget_helper_->CreateNewWindow(params,
                                          peer_handle(),
                                          route_id,