Web applications need a way to communicate between two same domain tabs without polling LocalStorage and without hitting the disk.
It would be useful to have an in-memory get/set/compare_and_set hash table exposed to scripts running same domain tabs, that is discarded by the browser when those tabs are closed. Use cases: 1. Coordinate replication between tabs for an offline app, i.e. one tab takes responsibility for syncing a user's data to and from IndexedDB. 2. Sign out from one tab triggers sign out from all other tabs. 3. If something like LevelDB were exposed directly to JS, one could implement MVCC on top using the shared hash. 4. Library authors would be able to implement their own cross-tab postMessage. It's difficult to implement these use cases with LocalStorage, without a coarse resolution, and risky at that, due to the lack of compare and set primitive in LocalStorage.
