Add support for an inputFP in SkMixerColorFilter::asFragmentProcessor.

Change-Id: Ib7a0b26568947bc0ec377a6f7f81ddac2c7c2528
Bug: skia:10217
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/300649
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
4 files changed