Persist sessionStorage on disk.

content/browser/dom_storage/dom_storage_context_impl.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_BROWSER_DOM_STORAGE_DOM_STORAGE_CONTEXT_IMPL_H_
 #define CONTENT_BROWSER_DOM_STORAGE_DOM_STORAGE_CONTEXT_IMPL_H_
 
 #include "base/memory/ref_counted.h"
 #include "content/public/browser/dom_storage_context.h"
 
 class FilePath;
 
 namespace quota {
 class SpecialStoragePolicy;
 }
 
 // This is owned by BrowserContext (aka Profile) and encapsulates all
 // per-profile dom storage state.
 class CONTENT_EXPORT DOMStorageContextImpl :
     NON_EXPORTED_BASE(public content::DOMStorageContext),
     public base::RefCountedThreadSafe<DOMStorageContextImpl> {
  public:
   // If |data_path| is empty, nothing will be saved to disk.
   DOMStorageContextImpl(const FilePath& data_path,
-                        quota::SpecialStoragePolicy* special_storage_policy);
+                        quota::SpecialStoragePolicy* special_storage_policy,
+                        bool save_session_storage_on_disk);
 
   // DOMStorageContext implementation.
   virtual void GetUsageInfo(const GetUsageInfoCallback& callback) OVERRIDE;
   virtual void DeleteOrigin(const GURL& origin) OVERRIDE;
   virtual scoped_refptr<content::SessionStorageNamespace>
       RecreateSessionStorage(const std::string& persistent_id) OVERRIDE;
+  virtual void StartScavengingUnusedSessionStorage() OVERRIDE;
 
   // Called to free up memory that's not strictly needed.
   void PurgeMemory();
 
   // Used by content settings to alter the behavior around
   // what data to keep and what data to discard at shutdown.
   // The policy is not so straight forward to describe, see
   // the implementation for details.
   void SetForceKeepSessionState();
 
   // Called when the BrowserContext/Profile is going away.
   void Shutdown();
 
  private:
   friend class DOMStorageMessageFilter;  // for access to context()
   friend class SessionStorageNamespaceImpl;  // ditto
   friend class base::RefCountedThreadSafe<DOMStorageContextImpl>;
 
   virtual ~DOMStorageContextImpl();
   dom_storage::DomStorageContext* context() const { return context_.get(); }
 
   scoped_refptr<dom_storage::DomStorageContext> context_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(DOMStorageContextImpl);
 };
 
 #endif  // CONTENT_BROWSER_DOM_STORAGE_DOM_STORAGE_CONTEXT_IMPL_H_