[Resource Timing] Initiator Types

I have a few questions on the initiator types:

INITIATOR_AUDIO
INITIATOR_VIDEO

These ones are a little tricky to time. They don't necessarily load like
other resources. Sometimes they're never-ending streams. Sometimes they're
only partially loaded (user skips ahead). And sometimes they're only loaded
lazily when the user hits play. I could imagine a situation where we had to
open multiple connections too, which would make some of the timing
attributes ambiguous. What are we supposed to do in these cases?

It's possible that Resource Timing isn't sufficient for describing these
elements. Maybe they should have they're own class of entries on the
Performance Timeline.

INITIATOR_SVG

This one says it's used if "the initiator is the <svg> element," but there's
no way for the <svg> element to load something. Should this instead read
"elements in the SVG namespace?" That would pick up SVG's <script> or
<font-face-uri> for instance.

James