Simplify GetRuntimeBlendForBlendMode.

Now that we support sampling from an SkBlender inside a Runtime Effect,
we can leverage that to reuse the blends from SkBlender::Mode. This lets
us avoid hard-coding copies of every built-in blend function.

Change-Id: I51f380490611fbde943c16648999b4fd4e6a14a9
Bug: skia:12257, skia:12085
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/434472
Commit-Queue: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
2 files changed