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In network process, WebStorage data is managed by WebKit::StorageManager class. Each StorageManager owns one or many StorageNameSpaces, and each StorageNamespace owns one or more StorageAreas. Each StorageArea corresponds to one storage map (one localStorage or sessionStorage object), using either a SQLite database or a in-memory map as backend. Now that we have NetworkStorageManager, which manages storage by origin. We can merge StorageManager with NetworkStorageManager, since localStorage and sessionStorage are not shared between different origins.


  • NetworkStorageManager (manage storage for a session, owns one or more OriginStorageManagers)
  • OriginStorageManager (manage storage for an origin, owns one LocalStorageManager and one SessionStorageManager)
  • LocalStorageManager / SessionStorageManager (manage LocalStorage and SessionStorage, owns one or more StorageAreaBases)
  • MemoryStorageArea / SQLiteStorageArea (inherits StorageAreaBases; manage one local or session storage, like Webkit::StorageArea)

Storage Manager


The StorageNamespace layer was removed. For SessionStorage, different StorageNamespaces means different web pages, and same origin can have different sessionStorages on different pages, so we keep a StorageNamespace <=> StorageArea map in SessionStorageManager. For LocalStorage, different StorageNamespaces means different page groups. Our original plan was the same origin can have different localStorages in different page groups, but our old implementation actually made all page groups point to the same database file. To keep existing behavior that all page groups with same origin share the storage, we now keep one local StorageArea and one transient StorageArea per LocalStorageManager.