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

gm/drawatlas.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "gm.h"
 #include "SkCanvas.h"
 #include "SkRSXform.h"
 #include "SkSurface.h"
 
 class DrawAtlasGM : public skiagm::GM {
     static sk_sp<SkImage> MakeAtlas(SkCanvas* caller, const SkRect& target) {
         SkImageInfo info = SkImageInfo::MakeN32Premul(100, 100);
         auto surface(caller->makeSurface(info));
         if (nullptr == surface) {
             surface = SkSurface::MakeRaster(info);
         }
         SkCanvas* canvas = surface->getCanvas();
         // draw red everywhere, but we don't expect to see it in the draw, testing the notion
         // that drawAtlas draws a subset-region of the atlas.
         canvas->clear(SK_ColorRED);
 
         SkPaint paint;
-        paint.setXfermodeMode(SkXfermode::kClear_Mode);
+        paint.setBlendMode(SkBlendMode::kClear);
         SkRect r(target);
         r.inset(-1, -1);
         // zero out a place (with a 1-pixel border) to land our drawing.
         canvas->drawRect(r, paint);
-        paint.setXfermode(nullptr);
+        paint.setBlendMode(SkBlendMode::kSrcOver);
         paint.setColor(SK_ColorBLUE);
         paint.setAntiAlias(true);
         canvas->drawOval(target, paint);
         return surface->makeImageSnapshot();
     }
 
 public:
     DrawAtlasGM() {}
 
 protected:
@@ skipping 119 matching lines @@
     SkPath path;
     path.addOval(SkRect::MakeXYWH(160, 160, 540, 540));
 
     draw_text_on_path_rigid(canvas, text0, N, pos, path, paint);
 
     paint.setStyle(SkPaint::kStroke_Style);
     canvas->drawPath(path, paint);
 }