Revert of SoftLight with SkPMFloat

src/opts/SkXfermode_opts_SSE2.cpp

Index: src/opts/SkXfermode_opts_SSE2.cpp
diff --git a/src/opts/SkXfermode_opts_SSE2.cpp b/src/opts/SkXfermode_opts_SSE2.cpp
index 2024a175a889760ed1c844fb22c72d8fdebf8fcf..ca26263727238d83dbf5b3cec2c81bbc7aeea51c 100644
--- a/src/opts/SkXfermode_opts_SSE2.cpp
+++ b/src/opts/SkXfermode_opts_SSE2.cpp
@@ -516,13 +516,15 @@
                                                          SkXfermode::Mode mode) {
     SkXfermodeProcSIMD proc = nullptr;
     switch (mode) {
-        // TODO(mtklein): Sk4pxXfermode has these now.  Clean up the whole file!
+        // TODO(mtklein): Sk4pxXfermode has these now.  Clean up.
         case SkProcCoeffXfermode::kOverlay_Mode:    proc =    overlay_modeproc_SSE2; break;
         case SkProcCoeffXfermode::kDarken_Mode:     proc =     darken_modeproc_SSE2; break;
         case SkProcCoeffXfermode::kLighten_Mode:    proc =    lighten_modeproc_SSE2; break;
         case SkProcCoeffXfermode::kHardLight_Mode:  proc =  hardlight_modeproc_SSE2; break;
         case SkProcCoeffXfermode::kColorDodge_Mode: proc = colordodge_modeproc_SSE2; break;
         case SkProcCoeffXfermode::kColorBurn_Mode:  proc =  colorburn_modeproc_SSE2; break;
+
+        // TODO(mtklein): implement this with SkPMFloat.
         case SkProcCoeffXfermode::kSoftLight_Mode:  proc =  softlight_modeproc_SSE2; break;
         default: break;
     }