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

This reverts commit c245574ba3d0e2ade6c94b2812de3baa383bf4c4.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2396953002

TBR=

Review-Url: https://codereview.chromium.org/2396953002
diff --git a/samplecode/SampleFatBits.cpp b/samplecode/SampleFatBits.cpp
index 8da6058..82eb25f 100644
--- a/samplecode/SampleFatBits.cpp
+++ b/samplecode/SampleFatBits.cpp
@@ -163,7 +163,7 @@
         canvas->restore();
 
         SkPaint paint;
-        paint.setXfermodeMode(SkXfermode::kClear_Mode);
+        paint.setBlendMode(SkBlendMode::kClear);
         for (int iy = 1; iy < fH; ++iy) {
             SkScalar y = SkIntToScalar(iy * fZoom);
             canvas->drawLine(0, y - SK_ScalarHalf, 999, y - SK_ScalarHalf, paint);