After BrowserStack removed & restored Safari 7.0 in the API, it started failing the createHTMLDocument support test. This is unrelated to jQuery Core code changes, I've restarted an older job and it failed now even though it was successful initially.

The user agents of the browsers differ, the old one that succeeded:

Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_5) AppleWebKit/537.78.2 (KHTML, like Gecko) Version/7.0.6 Safari/537.78.2

The new one that fails:

Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_5) AppleWebKit/600.8.9 (KHTML, like Gecko) Version/7.0.6 Safari/537.78.2

Notice the AppleWebKit/537.78.2 vs. AppleWebKit/600.8.9 token.

EDIT: for comparison, see the successful run on the "old" Safari 7.0: http://swarm.jquery.org/result/585139 and the broken one on the "new" Safari 7.0: http://swarm.jquery.org/result/643947.