Make SubpixelAlignment public

And, change the logic to handle NaN and Inf.
Small cleanup.

BUG=skia:7515

Change-Id: Ib02ad8f4bc66df57d226d4440ef6214fd2f813d6
Reviewed-on: https://skia-review.googlesource.com/113742
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Herb Derby <herb@google.com>
1 file changed