deleteDatabase() success should be IDBVersionChangeEvent [Tests]

New tests only. Originally reviewed as part of crrev.com/235493003
but split out for a 3-part landing (blink, chromium, tests).

TBR=dgrogan@chromium.org,cmumford@chromium.org
BUG=362251

Review URL: https://codereview.chromium.org/235933010

git-svn-id: svn://svn.chromium.org/blink/trunk@171507 bbb929c8-8fbe-4397-9dbb-9b2b20218538