3-15% speedup to HardLight / Overlay xfermodes.

src/opts/Sk4px_none.h

Index: src/opts/Sk4px_none.h
diff --git a/src/opts/Sk4px_none.h b/src/opts/Sk4px_none.h
index ce2f8452e55d9127e9405781a29eb8bc72f25d97..ba13e58fb50c6f6d5642194da6142e734e92109a 100644
--- a/src/opts/Sk4px_none.h
+++ b/src/opts/Sk4px_none.h
@@ -48,6 +48,8 @@ inline Sk4px::Wide Sk4px::widenLo() const {
 
 inline Sk4px::Wide Sk4px::widenHi() const { return this->widenLo() << 8; }
 
+inline Sk4px::Wide Sk4px::widenLoHi() const { return this->widenLo() + this->widenHi(); }
+
 inline Sk4px::Wide Sk4px::mulWiden(const Sk16b& other) const {
     return this->widenLo() * Sk4px(other).widenLo();
 }