The following tests are flaky on Mac Release:

- storage/indexeddb/basics-shared-workers.html
- storage/indexeddb/cursor-advance-workers.html
- storage/indexeddb/objectstore-basics-workers.html
- storage/indexeddb/transaction-complete-workers.html
- http/tests/serviceworker/indexeddb.html

BUG=393832
TBR=falken@chromium.org

Review URL: https://codereview.chromium.org/394663005

git-svn-id: svn://svn.chromium.org/blink/trunk@178127 bbb929c8-8fbe-4397-9dbb-9b2b20218538