Automatic update from web-platform-testsExperimental Priority Hints support on fetch() API Adding support for Priority Hints on the fetch() API under an experimental flag. This adds the notion of importance to core/fetch code, and adds a new member to the RequestInit dictionary to communicate developer-specified "importance" downstream. R=kinuko@chromium.org, kouhei@chromium.org, yhirano@chromium.org, yoav@yoav.ws Bug: 821464 Change-Id: Ib96a128d77004029e86122c07552250c697dea5f Reviewed-on: https://chromium-review.googlesource.com/1084063 Reviewed-by: Yutaka Hirano <yhirano@chromium.org> Reviewed-by: Yoav Weiss <yoav@yoav.ws> Commit-Queue: Dominic Farolino <domfarolino@gmail.com> Cr-Commit-Position: refs/heads/master@{#564410} -- wpt-commits: dae7535c0428fbf057a5c39f324d5a3f47ba64c7 wpt-pr: 11317