Unify some SkNx code

src/opts/SkXfermode_opts.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef Sk4pxXfermode_DEFINED
 #define Sk4pxXfermode_DEFINED
 
@@ skipping 247 matching lines @@
         for (int i = 0; i < n; i++) {
             SkPMColor dst32 = SkPixel16ToPixel32(dst[i]);
             dst32 = aa ? this->xfer32(dst32, src[i], aa[i])
                        : this->xfer32(dst32, src[i]);
             dst[i] = SkPixel32ToPixel16(dst32);
         }
     }
 
 private:
     static Sk4f Load(SkPMColor c) {
-        return Sk4f::FromBytes((uint8_t*)&c) * Sk4f(1.0f/255);
+        return SkNx_cast<float>(Sk4b::Load((uint8_t*)&c)) * Sk4f(1.0f/255);
     }
     static SkPMColor Round(const Sk4f& f) {
         SkPMColor c;
-        (f * Sk4f(255) + Sk4f(0.5f)).toBytes((uint8_t*)&c);
+        SkNx_cast<uint8_t>(f * Sk4f(255) + Sk4f(0.5f)).store((uint8_t*)&c);
         return c;
     }
     inline SkPMColor xfer32(SkPMColor dst, SkPMColor src) const {
         return Round(fProcF(Load(dst), Load(src)));
     }
 
     inline SkPMColor xfer32(SkPMColor dst, SkPMColor src, SkAlpha aa) const {
         Sk4f s(Load(src)),
              d(Load(dst)),
              b(fProcF(d,s));
@@ skipping 47 matching lines @@
     #undef CASE
 
         default: break;
     }
     return nullptr;
 }
 
 } // namespace SK_OPTS_NS
 
 #endif//Sk4pxXfermode_DEFINED