Only set dw antialias mode to grayscale for A8.

The previous code would also set 'grayscale' for aliased which would
then cause the code to use the new renderer, which has issues with
aliased glyphs.

BUG=skia:5416

Change-Id: Ia856322b59d0eba258522d73c3a4d827ab4429e1
Reviewed-on: https://skia-review.googlesource.com/9834
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
1 file changed