[canvaskit] Fix color opaqueness

Bug: skia:9800
Change-Id: I61d50df47467dbcee6d90fd636749a4d19c4da8f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/265957
Reviewed-by: Brian Osman <brianosman@google.com>
3 files changed