Spec change: https://github.com/whatwg/fetch/pull/560.
Security issues to pay attention to: https://github.com/whatwg/fetch/issues/144#issuecomment-368040980
This spec change means that rage requests (such as those from media elements) are allowed to pass through a service worker as long as they aren't modified. This fixes a long standing issue where media elements behave oddly if intercepted by a service worker (as the range headers were lost).
How media elements ingest partial responses remains unspecified for now. See the attacks in https://github.com/whatwg/fetch/issues/144#issuecomment-368040980 & their mitigations. Attack 4 is already covered in the tests.
This would solve https://bugs.webkit.org/show_bug.cgi?id=184447
*** This bug has been marked as a duplicate of bug 184447 ***