Shaping inside fonts relies on the correct glyphIDs being used. However, we replace a bunch of glyphs with the zero width space glyph, which fonts won't expect.
*** Bug 215643 has been marked as a duplicate of this bug. ***
This will fix https://bugs.webkit.org/show_bug.cgi?id=215643
Actually, let's reverse-dup.
*** This bug has been marked as a duplicate of bug 215643 ***
rdar://56355689 has some more.