[html-tests] Unbreak and rename the autoplay vs. preload test (#681)

It was broken since loadstart is fired regardless of preload.
A later event must be used, e.g. playing.

Test both orders of setting the attributes.
Blink fails with one order but not the other.

View on GitHub: https://github.com/w3c/web-platform-tests/pull/681

Received on Saturday, 22 February 2014 19:07:27 UTC