For an explanation of what TSR is, see ComputeDSR#computeNodeDSR()

TSR info on all these tags are only valid for the opening tag. (closing tags dont have attrs since tree-builder strips them and adds meta-tags tracking the corresponding TSR)

On other tags, a, hr, br, meta-marker tags, the tsr spans the entire DOM, not just the tag.

This code is not in WikitextConstants because this information is Parsoid-implementation-specific.