Text mask painting.
Created attachment 441532 [details] Patch
Created attachment 441535 [details] Patch
Created attachment 441536 [details] Patch
Committed r284334 (243129@main): <https://commits.webkit.org/243129@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 441536 [details].
<rdar://problem/84347147>