it maps to RenderStyle::collapseWhiteSpace which is also misleading a bit (1. tabs are not preserved, 2. subsequent whitespace content is collapsed)
Created attachment 416027 [details] Patch
Committed r270707: <https://trac.webkit.org/changeset/270707> All reviewed patches have been landed. Closing bug and clearing flags on attachment 416027 [details].
<rdar://problem/72236772>