Sk4px: SrcATop, DstATop, Xor, Multiply

SSE runs 2-3x faster (than 4f), NEON runs 1.2-1.4x faster (than existing NEON).

Small diffs on {aarectmodes, imagefilters_xfermodes, hairmodes, mixed_xfermodes} only on AA edges due to precision drop.

BUG=skia:

Review URL: https://codereview.chromium.org/1132853005
2 files changed