Other engines, like gecko, keep track of a range of code points that there is no Glyph Data available. For example, code points within the PUA block. We could do something similar and run a performance A/B test on it.
Same as bug 266697?
Yeah, not sure what happened. I'll close this one since the other already has an associated radar. Thank you. *** This bug has been marked as a duplicate of bug 266697 ***