service worker: Upstream sandboxed iframe test to WPT.

This test is a fine subject matter for WPT.

Bug: 486308, 688116
Change-Id: I91d8484286094c695fe2219f0c017e25e8bfd34c
Reviewed-on: https://chromium-review.googlesource.com/759168
Reviewed-by: Tsuyoshi Horo <horo@chromium.org>
Commit-Queue: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#515030}
5 files changed