Use specialized multitexture lookup for LCD SDF text.

Right now we do three multitexture lookups for LCD, which means three
separate if-then-else statements. This CL rolls the LCD work into
the if-then-else statement so we only have one.

Change-Id: Ic7d203462fb02e0e51b7c2e62e6b31b7b103bacf
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/854717
Reviewed-by: Brian Osman <brianosman@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
3 files changed