Bug 984048 - Patch 4 - Handle parse and uncaught errors. r=khuey

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extra : rebase_source : 9cc36dea950be96fba079877c2d67b76f8383635
Bug 984048 - Patch 5 - ServiceWorker [[Install]] algorithm. r=ehsan, khuey

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extra : rebase_source : 5f9d890c655d7f5e77851a8a3bd6b6fd3f9bf108