Support the CORS preflight cache on workers.

Bug: 443374

Change-Id: Icc8b2633530710fe9aa380ca94751ba67255f994
Reviewed-on: https://chromium-review.googlesource.com/627939
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Takeshi Yoshino <tyoshino@chromium.org>
Commit-Queue: Tsuyoshi Horo <horo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#498045}
5 files changed