DOMRect was changed sufficiently that ClientRect can be made a simple alias of it.
Rough steps:
1. Sync DOMRect with https://drafts.fxtf.org/geometry/#DOMRect (it's not shipped, so entirely safe)
2. Remove the ClientRect code in favor of an alias for DOMRect
3. Use Sequence instead of ClientRectList code
4. Watch for regressions, revert, and tweak the spec until it works
Comment 1 by fs...@chromium.org
, May 8 2017