Replace GrExtractAlphaFragmentProcessor with DstIn compose processor

src/core/SkShader.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 "SkAtomics.h"
 #include "SkBitmapProcShader.h"
 #include "SkColorShader.h"
@@ skipping 198 matching lines @@
 SkShader::GradientType SkShader::asAGradient(GradientInfo* info) const {
     return kNone_GradientType;
 }
 
 const GrFragmentProcessor* SkShader::asFragmentProcessor(GrContext*, const SkMatrix&,
                                                          const SkMatrix*, SkFilterQuality,
                                                          GrProcessorDataManager*)  const {
     return nullptr;
 }
 
+#if SK_SUPPORT_GPU
+
+#include "effects/GrXfermodeFragmentProcessor.h"
+
+const GrFragmentProcessor* SkShader::MulFragmentProcesorOuputByInputAlpha(
+    const GrFragmentProcessor* fp) {
+    return GrXfermodeFragmentProcessor::CreateFromDstProcessor(fp, SkXfermode::kDstIn_Mode);
+}
+
+#endif
+
 SkShader* SkShader::refAsALocalMatrixShader(SkMatrix*) const {
     return nullptr;
 }
 
 SkShader* SkShader::CreateEmptyShader() { return new SkEmptyShader; }
 
 SkShader* SkShader::CreateColorShader(SkColor color) { return new SkColorShader(color); }
 
 SkShader* SkShader::CreateBitmapShader(const SkBitmap& src, TileMode tmx, TileMode tmy,
                                        const SkMatrix* localMatrix) {
@@ skipping 135 matching lines @@
 #include "SkEmptyShader.h"
 
 void SkEmptyShader::toString(SkString* str) const {
     str->append("SkEmptyShader: (");
 
     this->INHERITED::toString(str);
 
     str->append(")");
 }
 #endif