Update some Sk4px APIs.

src/opts/Sk4px_none.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.
  */
 
 #include "SkUtils.h"
 
 namespace { // See Sk4px.h
 
 static_assert(sizeof(Sk4px) == 16, "This file uses memcpy / sk_memset32, so exact size matters.");
 
-inline Sk4px::Sk4px(SkPMColor px) {
-    sk_memset32((uint32_t*)this, px, 4);
+inline Sk4px Sk4px::DupPMColor(SkPMColor px) {
+    Sk4px px4 = Sk16b();
+    sk_memset32((uint32_t*)&px4, px, 4);
+    return px4;
 }
 
 inline Sk4px Sk4px::Load4(const SkPMColor px[4]) {
     Sk4px px4 = Sk16b();
     memcpy(&px4, px, 16);
     return px4;
 }
 
 inline Sk4px Sk4px::Load2(const SkPMColor px[2]) {
     Sk4px px2 = Sk16b();
@@ skipping 64 matching lines @@
 
 inline Sk4px Sk4px::zeroColors() const {
     static_assert(SK_A32_SHIFT == 24, "This method assumes little-endian.");
     return Sk16b(0,0,0, this->kth< 3>(),
                  0,0,0, this->kth< 7>(),
                  0,0,0, this->kth<11>(),
                  0,0,0, this->kth<15>());
 }
 
 }  // namespace