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

src/core/SkBlitter_A8.cpp

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "SkCoreBlitters.h"
 #include "SkColorPriv.h"
@@ skipping 212 matching lines @@
         }
     }
 }
 
 ///////////////////////////////////////////////////////////////////////
 
 SkA8_Shader_Blitter::SkA8_Shader_Blitter(const SkPixmap& device, const SkPaint& paint,
                                          SkShader::Context* shaderContext)
     : INHERITED(device, paint, shaderContext)
 {
-    if ((fXfermode = paint.getXfermode()) != nullptr) {
-        fXfermode->ref();
-        SkASSERT(fShaderContext);
-    }
+    fXfermode = SkXfermode::Peek(paint.getBlendMode());
+    SkASSERT(!fXfermode || fShaderContext);
 
     int width = device.width();
     fBuffer = (SkPMColor*)sk_malloc_throw(sizeof(SkPMColor) * (width + (SkAlign4(width) >> 2)));
     fAAExpand = (uint8_t*)(fBuffer + width);
 }
 
 SkA8_Shader_Blitter::~SkA8_Shader_Blitter() {
-    if (fXfermode) SkSafeUnref(fXfermode);
     sk_free(fBuffer);
 }
 
 void SkA8_Shader_Blitter::blitH(int x, int y, int width) {
     SkASSERT(x >= 0 && y >= 0 &&
              (unsigned)(x + width) <= (unsigned)fDevice.width());
 
     uint8_t* device = fDevice.writable_addr8(x, y);
     SkShader::Context* shaderContext = fShaderContext;
 
@@ skipping 93 matching lines @@
         device += fDevice.rowBytes();
         alpha += mask.fRowBytes;
     }
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 SkA8_Coverage_Blitter::SkA8_Coverage_Blitter(const SkPixmap& device,
                              const SkPaint& paint) : SkRasterBlitter(device) {
     SkASSERT(nullptr == paint.getShader());
-    SkASSERT(nullptr == paint.getXfermode());
+    SkASSERT(paint.isSrcOver());
     SkASSERT(nullptr == paint.getColorFilter());
 }
 
 void SkA8_Coverage_Blitter::blitAntiH(int x, int y, const SkAlpha antialias[],
                                       const int16_t runs[]) {
     uint8_t* device = fDevice.writable_addr8(x, y);
     SkDEBUGCODE(int totalCount = 0;)
 
     for (;;) {
         int count = runs[0];
@@ skipping 55 matching lines @@
     while (--height >= 0) {
         memcpy(dst, src, width);
         dst += dstRB;
         src += srcRB;
     }
 }
 
 const SkPixmap* SkA8_Coverage_Blitter::justAnOpaqueColor(uint32_t*) {
     return nullptr;
 }