Move Sk4px Xfermode code to a header so we can use it twice.

src/opts/SkXfermode_opts_arm_neon.cpp

+// Copyright 2013 unknown
+
 #include "SkXfermode.h"
 #include "SkXfermode_proccoeff.h"
 #include "SkColorPriv.h"
 
 #include <arm_neon.h>
 #include "SkColor_opts_neon.h"
 #include "SkXfermode_opts_arm_neon.h"
+#include "Sk4pxXfermode.h"
 
 #define SkAlphaMulAlpha(a, b)   SkMulDiv255Round(a, b)
 
 
 ////////////////////////////////////////////////////////////////////////////////
 // NEONized skia functions
 ////////////////////////////////////////////////////////////////////////////////
 
 static inline uint8x8_t SkAlphaMulAlpha_neon8(uint8x8_t color, uint8x8_t alpha) {
     uint16x8_t tmp;
@@ skipping 985 matching lines @@
     NULL, // kLuminosity_Mode
 };
 
 SK_COMPILE_ASSERT(
     SK_ARRAY_COUNT(gNEONXfermodeProcs1) == SkXfermode::kLastMode + 1,
     mode1_count_arm
 );
 
 SkProcCoeffXfermode* SkPlatformXfermodeFactory_impl_neon(const ProcCoeff& rec,
                                                          SkXfermode::Mode mode) {
-
-    void* procSIMD = reinterpret_cast<void*>(gNEONXfermodeProcs[mode]);
-
-    if (procSIMD != NULL) {
-        return SkNEW_ARGS(SkNEONProcCoeffXfermode, (rec, mode, procSIMD));
+    if (auto xfermode = SkCreate4pxXfermode(rec, mode)) {
+        return xfermode;
+    }
+    if (auto proc = gNEONXfermodeProcs[mode]) {
+        return SkNEW_ARGS(SkNEONProcCoeffXfermode, (rec, mode, (void*)proc));
     }
     return NULL;
 }
 
 SkXfermodeProc SkPlatformXfermodeProcFactory_impl_neon(SkXfermode::Mode mode) {
     return gNEONXfermodeProcs1[mode];
 }