Support sRGB dsts in opt code

src/opts/SkNx_sse.h

Index: src/opts/SkNx_sse.h
diff --git a/src/opts/SkNx_sse.h b/src/opts/SkNx_sse.h
index bdc6d77ce728bbfd74b0d280800b0fe250e690ff..9751c4db9141246681d8905bbaf2f5220fb293c2 100644
--- a/src/opts/SkNx_sse.h
+++ b/src/opts/SkNx_sse.h
@@ -124,8 +124,12 @@ public:
     bool anyTrue() const { return 0x0000 != _mm_movemask_epi8(_mm_castps_si128(fVec)); }
 
     SkNx thenElse(const SkNx& t, const SkNx& e) const {
+#if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE41
+        return _mm_blendv_ps(e.fVec, t.fVec, fVec);
+#else
         return _mm_or_ps(_mm_and_ps   (fVec, t.fVec),
                          _mm_andnot_ps(fVec, e.fVec));
+#endif
     }
 
     __m128 fVec;