Port SkXfermode opts to SkOpts.h

src/opts/SkOpts_sse2.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 "SkOpts.h"
+#include "SkXfermode_opts.h"
 
 namespace sse2 {  // This helps identify methods from this file when debugging / profiling.
 
 static void memset16(uint16_t* dst, uint16_t val, int n) {
     auto dst8 = (__m128i*)dst;
     auto val8 = _mm_set1_epi16(val);
     for ( ; n >= 8; n -= 8) {
         _mm_storeu_si128(dst8++, val8);
     }
     dst = (uint16_t*)dst8;
@@ skipping 23 matching lines @@
     }
     if (n & 1) {
         *dst = val;
     }
 }
 
 }  // namespace sse2
 
 namespace SkOpts {
     void Init_sse2() {
-        memset16 = sse2::memset16;
-        memset32 = sse2::memset32;
+        memset16        = sse2::memset16;
+        memset32        = sse2::memset32;
+        create_xfermode = SkCreate4pxXfermode;
     }
 }