Test partitioned cookies/service worker interaction and fix DCHECK

[chromium-wpt-export-bot]

This CL adds a WPT which exercises the interaction between partitioned service workers and partitioned cookies.

When 3P storage partitioning is enabled, partitioned cookies should only be visible to partitioned workers whose StorageKey's top-level site matches the CookiePartitionKey.

This test only covers getting/setting cookies in workers, it does not exercise cookie change listeners being partitioned correctly. This is still a WIP, https://crrev.com/c/3236772.

Bug:1225444 Change-Id: Id101b4fa48bed46605fe95f7ef2b1d2463f9301a Reviewed-on: https://chromium-review.googlesource.com/3674179 WPT-Export-Revision: af805fd085272cafb7a0f787d9bc7c62f73f6744