[ResourceTiming] initiator types

Is there a use-case for the current hard-coded groupings in the list of
initiatorTypes? Could we simplify this bit by defining initiatorType in
terms of the initiator?

If the initiator is an element, the initiatorType is the element's
localname. If the initiator is a JavaScript object, the initiatorType is
the name of the object's constructor. Resources downloaded via CSS url() or
@import would be have the "link" or "style" initiatorType depending on
which element the CSS was loaded from.

I think that will be more intuitive for web developers. They don't need to
understand, for example, that all svg element types that load resources are
grouped under svg or that iframe resources are loaded as subdocuments. It's
a simple rule and they don't need to consult the spec to remember how it
works each time. Web developers should not be expected to read specs.

Could we also get rid of "other" as an initiatorType as the definition
would cover all cases. What's the use-case for "other"?

Ojan