Revert of SoftLight with SkPMFloat

src/core/Sk4pxXfermode.h

Index: src/core/Sk4pxXfermode.h
diff --git a/src/core/Sk4pxXfermode.h b/src/core/Sk4pxXfermode.h
index 28fd9f1e7b478758106878715c2442bed4e8be75..b58718304610d7ff2decfa08de4db2e291660887 100644
--- a/src/core/Sk4pxXfermode.h
+++ b/src/core/Sk4pxXfermode.h
@@ -140,31 +140,6 @@
                   (s == Sk4f(0)).thenElse(srcover,
                                           otherwise));
     return srcover * SkPMFloat(1,0,0,0) + colors * SkPMFloat(0,1,1,1);
-}
-XFERMODE(SoftLight) {
-    auto sa = s.alphas(),
-         da = d.alphas(),
-         isa = Sk4f(1)-sa,
-         ida = Sk4f(1)-da;
-
-    // Some common terms.
-    auto m  = (da > Sk4f(0)).thenElse(d / da, Sk4f(0)),
-         s2 = Sk4f(2)*s,
-         m4 = Sk4f(4)*m;
-
-    // The logic forks three ways:
-    //    1. dark src?
-    //    2. light src, dark dst?
-    //    3. light src, light dst?
-    auto darkSrc = d*(sa + (s2 - sa)*(Sk4f(1) - m)),        // Used in case 1.
-         darkDst = (m4*m4 + m4)*(m - Sk4f(1)) + Sk4f(7)*m,  // Used in case 2.
-         liteDst = m.sqrt() - m,                            // Used in case 3.
-         liteSrc = d*sa + da*(s2-sa)*(Sk4f(4)*d < da).thenElse(darkDst, liteDst); // Case 2 or 3?
-
-    auto alpha  = s + d*isa;
-    auto colors = s*ida + d*isa + (s2 < sa).thenElse(darkSrc, liteSrc);           // Case 1 or 2/3?
-
-    return alpha * SkPMFloat(1,0,0,0) + colors * SkPMFloat(0,1,1,1);
 }
 #undef XFERMODE
 
@@ -269,7 +244,6 @@
 
         case SkXfermode::kColorDodge_Mode: return SkTPMFloatXfermode<ColorDodge>::Create(rec);
         case SkXfermode::kColorBurn_Mode:  return SkTPMFloatXfermode<ColorBurn>::Create(rec);
-        case SkXfermode::kSoftLight_Mode:  return SkTPMFloatXfermode<SoftLight>::Create(rec);
 #endif
         default: break;
     }