Remove paint-color transform in working-format color filter

Includes a comment explaining the rationale. Note that the previous code
was actually *wrong*, too. We were treating the color as originally
premul (it wasn't), and transforming to an unknown alpha type, which
would have confused any code using it.

Change-Id: I7f6c3dad84944ba4ab47c0776f400dbb1a0a1f07
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/757336
Reviewed-by: John Stiles <johnstiles@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
1 file changed