Unify some SkNx code

tests/SkNxTest.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "Sk4px.h"
 #include "SkNx.h"
 #include "SkRandom.h"
@@ skipping 189 matching lines @@
     };
     auto packed = Sk4px::Load4(colors);
 
     auto wideLo = packed.widenLo(),
          wideHi = packed.widenHi(),
          wideLoHi    = packed.widenLoHi(),
          wideLoHiAlt = wideLo + wideHi;
     REPORTER_ASSERT(r, 0 == memcmp(&wideLoHi, &wideLoHiAlt, sizeof(wideLoHi)));
 }
 
-DEF_TEST(Sk4f_toBytes, r) {
-    uint8_t bytes[4];
-
-    // toBytes truncates, not rounds.
-    Sk4f(0.7f).toBytes(bytes);
-    REPORTER_ASSERT(r, bytes[0] == 0);
-
-    // Clamping edge cases.
-    Sk4f(-2.0f, -0.7f, 255.9f, 256.0f).toBytes(bytes);
-    REPORTER_ASSERT(r, bytes[0] == 0);
-    REPORTER_ASSERT(r, bytes[1] == 0);
-    REPORTER_ASSERT(r, bytes[2] == 255);
-    REPORTER_ASSERT(r, bytes[3] == 255);
-}
-
 DEF_TEST(SkNx_cast, r) {
     Sk4f fs(-1.7f, -1.4f, 0.5f, 1.9f);
     Sk4i is = SkNx_cast<int>(fs);
 
     REPORTER_ASSERT(r, is.kth<0>() == -1);
     REPORTER_ASSERT(r, is.kth<1>() == -1);
     REPORTER_ASSERT(r, is.kth<2>() ==  0);
     REPORTER_ASSERT(r, is.kth<3>() ==  1);
 }