Simplify flattening to just write enough to call the factory

src/opts/SkXfermode_opts_arm_neon.cpp

 #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"
 
 #define SkAlphaMulAlpha(a, b)   SkMulDiv255Round(a, b)
 
@@ skipping 725 matching lines @@
 
     return ret;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 
 typedef uint8x8x4_t (*SkXfermodeProcSIMD)(uint8x8x4_t src, uint8x8x4_t dst);
 
 extern SkXfermodeProcSIMD gNEONXfermodeProcs[];
 
-SkNEONProcCoeffXfermode::SkNEONProcCoeffXfermode(SkReadBuffer& buffer)
-        : INHERITED(buffer) {
+#ifdef SK_SUPPORT_LEGACY_DEEPFLATTENING
+SkNEONProcCoeffXfermode::SkNEONProcCoeffXfermode(SkReadBuffer& buffer) : INHERITED(buffer) {
     fProcSIMD = reinterpret_cast<void*>(gNEONXfermodeProcs[this->getMode()]);
 }
+#endif
 
 void SkNEONProcCoeffXfermode::xfer32(SkPMColor* SK_RESTRICT dst,
                                      const SkPMColor* SK_RESTRICT src, int count,
                                      const SkAlpha* SK_RESTRICT aa) const {
     SkASSERT(dst && src && count >= 0);
 
     SkXfermodeProc proc = this->getProc();
     SkXfermodeProcSIMD procSIMD = reinterpret_cast<SkXfermodeProcSIMD>(fProcSIMD);
     SkASSERT(procSIMD != NULL);
 
@@ skipping 259 matching lines @@
 
     if (procSIMD != NULL) {
         return SkNEW_ARGS(SkNEONProcCoeffXfermode, (rec, mode, procSIMD));
     }
     return NULL;
 }
 
 SkXfermodeProc SkPlatformXfermodeProcFactory_impl_neon(SkXfermode::Mode mode) {
     return gNEONXfermodeProcs1[mode];
 }