SVG <use> elements register themselves with the document when their shadow tree contents need updating, and this updating is done in Document::resolveStyle. For lazy HTML <input> element UA shadow trees (in bug 236747) we need something similar.
Created attachment 453254 [details] Patch
Created attachment 453257 [details] Patch for bug 236747 with dependencies for EWS
Created attachment 453258 [details] Patch
Comment on attachment 453257 [details] Patch for bug 236747 with dependencies for EWS (Attached this to the wrong bug, but I don't want to cancel the EWS jobs, so leaving it here for now.)
Created attachment 453309 [details] Patch
<rdar://problem/89517318>
Committed r290574 (247852@main): <https://commits.webkit.org/247852@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 453309 [details].