Revert[8] "replace SkXfermode obj with SkBlendMode enum in paints"

src/core/SkSpriteBlitter_RGB16.cpp

Index: src/core/SkSpriteBlitter_RGB16.cpp
diff --git a/src/core/SkSpriteBlitter_RGB16.cpp b/src/core/SkSpriteBlitter_RGB16.cpp
index 6c5a7cb130468ea63a0936e06d04ef91a23b9dc7..9df7dab48c4f22b3a27aac1b9290392b92ad4580 100644
--- a/src/core/SkSpriteBlitter_RGB16.cpp
+++ b/src/core/SkSpriteBlitter_RGB16.cpp
@@ -307,7 +307,7 @@ SkSpriteBlitter* SkSpriteBlitter::ChooseD16(const SkPixmap& source, const SkPain
     if (paint.getMaskFilter() != nullptr) { // may add cases for this
         return nullptr;
     }
-    if (paint.getXfermode() != nullptr) { // may add cases for this
+    if (!paint.isSrcOver()) { // may add cases for this
         return nullptr;
     }
     if (paint.getColorFilter() != nullptr) { // may add cases for this