The storage event is propagated as usual window event in a context <embed-page> with common scope.
Depend of scope attribute either src URL or name value is used to define <embed-page> common
scope instances.
Each <embed-page> instance listens for storage window event.
If event key matches the own prefix (made out of name, uid, or URL depend of scope )
, the event is dispatched by own EpaWindow instance triggering the listeners within <embed-page> context.