Cleanup for TextLine::getGlyphPositionAtCoordinate.

Rename a few variables to make existing issues apparent. Also fix
potential divide by zero.

Change-Id: I071c4958f6eb2dcb79d34b4be95f57a4bbcb7b32
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/298750
Reviewed-by: Julia Lavrova <jlavrova@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
1 file changed