e.g. when the style change diff is RepaintOnly we know that the content has not changed, so no need to re-check each glyphs.
<rdar://problem/67951360>
Created attachment 407488 [details] Patch
Committed r266291: <https://trac.webkit.org/changeset/266291> All reviewed patches have been landed. Closing bug and clearing flags on attachment 407488 [details].