fast/workers/storage/interrupt-database.html is flaky.

BUG=323858
TBR=eseidel@chromium.org,falken@chromium.org

Review URL: https://codereview.chromium.org/93553002

git-svn-id: svn://svn.chromium.org/blink/trunk@162793 bbb929c8-8fbe-4397-9dbb-9b2b20218538