Technical feature description:

Disable 'content type sniffing' for worker scripts only. That is, only allow execution from resources with a supported JavaScript content type. This edges us a little closer to the goal of never second-guessing the content type of a resource.


Eng owner: vogelheim@chromium.org, mkwst@chromium.org


Design doc:

  +--------------------------------------------------------------------
  |
  | In AllowedByNosniff:::MimeTypeAsScript (AllowedByNosniff.cpp),
  | hoist worker_global_scope to the top and use it in the first
  | if-condition, or something vaguely like that.
  |
  +--------------------------------------------------------------------


Metrics: 

This condition is presently covered by UseCounters, which indicate this would impact less than 0.01% of page loads.