Revert "IndexedDB: Ensure transactions created in microtasks are deactivated"

This timed out on the waterfall and is failing on unrelated tryjobs runs
as well.

TBR=jsbell@chromium.org
BUG=380910

Review URL: https://codereview.chromium.org/316383002

git-svn-id: svn://svn.chromium.org/blink/trunk@175615 bbb929c8-8fbe-4397-9dbb-9b2b20218538