Remove GrAAType::kMixedSamples Our only use case for mixed samples is stencil-then-cover. This mode is now handled by AATypeFlags::kMixedSampledStencilThenCover. Bug: skia: Change-Id: Id7431cf83ccb20752d1bc85c6ad41efe408e0359 Reviewed-on: https://skia-review.googlesource.com/c/skia/+/200841 Commit-Queue: Chris Dalton <csmartdalton@google.com> Reviewed-by: Brian Salomon <bsalomon@google.com>