Backed out 4 changesets (bug 982726) for the same serviceworker perma-fails it hit last time it landed.

Backed out changeset 9674f68df2e5 (bug 982726)
Backed out changeset 9d397edb8e9a (bug 982726)
Backed out changeset ebe7add5dd11 (bug 982726)
Backed out changeset 2771520aa1b9 (bug 982726)