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

src/effects/SkDropShadowImageFilter.cpp

Index: src/effects/SkDropShadowImageFilter.cpp
diff --git a/src/effects/SkDropShadowImageFilter.cpp b/src/effects/SkDropShadowImageFilter.cpp
index b4b8cac4f0c95a9b0f5b1e6b60d80bd345d9010a..cc43db7f08b2dad89ce6da12c177edbc3138d3d5 100644
--- a/src/effects/SkDropShadowImageFilter.cpp
+++ b/src/effects/SkDropShadowImageFilter.cpp
@@ -95,7 +95,6 @@ sk_sp<SkSpecialImage> SkDropShadowImageFilter::onFilterImage(SkSpecialImage* sou
     SkPaint paint;
     paint.setImageFilter(SkBlurImageFilter::Make(sigma.fX, sigma.fY, nullptr));
     paint.setColorFilter(SkColorFilter::MakeModeFilter(fColor, SkXfermode::kSrcIn_Mode));
-    paint.setXfermodeMode(SkXfermode::kSrcOver_Mode);
 
     SkVector offsetVec = SkVector::Make(fDx, fDy);
     ctx.ctm().mapVectors(&offsetVec, 1);