CacheStorage: Add test that drops ref during query.

Bug: 965087
Change-Id: I60a84ae30953f5dd72e84102331757382dfca649
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1621388
Commit-Queue: Ben Kelly <wanderview@chromium.org>
Reviewed-by: Josh Karlin <jkarlin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661853}
5 files changed