remove double compose: lerp and mode

Bug: skia:8937
Change-Id: I5b890c03b0451afe4cbeb6a264798ebbb09b9888
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/205346
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
Auto-Submit: Mike Reed <reed@google.com>
8 files changed