More valid input checking for text

Bug: oss-fuzz: 10620
Change-Id: Ied2acba93719691d9fb889a25936b1ceded75d3f
Reviewed-on: https://skia-review.googlesource.com/156580
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
1 file changed