Saturate glyph bounds

Instead of zeroing out the bounds of large glyphs, saturate the bounds.
This means extremely large glyphs don't simply disappear and the glyph
scaling code knows the difference between extremely large glyphs and
empty glyphs.

Bug: oss-fuzz:59903
Change-Id: Ic8c6bef1c05528d481e55afc5e5ed0c38de1bd3b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/776018
Commit-Queue: Ben Wagner <bungeman@google.com>
Reviewed-by: Herb Derby <herb@google.com>
9 files changed