Bug 833385 - Remove tracing printfs.
Bug 833385 - Remove commented-out code.

Humph says this is the way we want to do this, but there's a race
with getting added to the parent media element. If we figure that
out we can bring this back. We need to load when our src attribute
is updated iff we're attached to a media element.

Look at what the <source> element implementation does. It has
similar semantics.
Add periods to the end of comments.