Bug 1089778 - ServiceWorkerRegistration is keyed by scope for event dispatch and invalidation. r=baku

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extra : rebase_source : 70ddb441e8146836cb340bb61985f01f9cfc719c
Integrated ServiceWorkerGlobalScope::Update into the ServiceWorkerRegisterJob.
Fixes in ServiceWorkerGlobalScope.unregister implementation to prevent Promise release on wrong thread.