Fix the mess that has become of 428393. This started as a patch to switch QUnit package (which may not be the case any more), but has led to several unit test failures. It's unclear how these are related to the QUnit upgrade, but they need to be solved nonetheless.
Some problems have been fixed, such as tests testing the wrong things (like behaviour of HTMLMediaElement) and things not resetting properly between tests. There are still some issues remaining concerning Ajax requests (possibly with race conditions) and audio playback.