[html-tests] Merge and expand audio_004.htm and video_001.htm (#636)

The existing tests only test that the playing event is fired, also test
that for the other three events fired in the same section of the spec.

This revealed a bug in Blink/WebKit, where canplaythrough is fired before
play and playing.

View on GitHub: https://github.com/w3c/web-platform-tests/pull/636

Received on Saturday, 15 February 2014 16:17:10 UTC