Persist sessionStorage on disk.

content/public/browser/dom_storage_context.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_PUBLIC_BROWSER_DOM_STORAGE_CONTEXT_H_
 #define CONTENT_PUBLIC_BROWSER_DOM_STORAGE_CONTEXT_H_
 #pragma once
 
 #include <vector>
 
@@ skipping 21 matching lines @@
   // Deletes the local storage data for the given origin.
   virtual void DeleteOrigin(const GURL& origin) = 0;
 
   // Creates a SessionStorageNamespace with the given |persistent_id|. Used
   // after tabs are restored by session restore. When created, the
   // SessionStorageNamespace with the correct |persistent_id| will be
   // associated with the persisted sessionStorage data.
   virtual scoped_refptr<SessionStorageNamespace> RecreateSessionStorage(
       const std::string& persistent_id) = 0;
 
+  // Starts deleting sessionStorages which don't have an associated
+  // SessionStorageNamespace alive. Called when SessionStorageNamespaces have
+  // been created after a session restore, or a session restore won't happen.
+  virtual void StartScavengingUnusedSessionStorage() = 0;
+
  protected:
   virtual ~DOMStorageContext() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_DOM_STORAGE_CONTEXT_H_