Replace GrExtractAlphaFragmentProcessor with DstIn compose processor

src/effects/gradients/SkSweepGradient.cpp

Index: src/effects/gradients/SkSweepGradient.cpp
diff --git a/src/effects/gradients/SkSweepGradient.cpp b/src/effects/gradients/SkSweepGradient.cpp
index 40b0f8288bfadf81865fe8909b994340f0edc65a..bd97974f2f62796657243d6baaf96934102038bc 100644
--- a/src/effects/gradients/SkSweepGradient.cpp
+++ b/src/effects/gradients/SkSweepGradient.cpp
@@ -167,7 +167,6 @@ void SkSweepGradient::SweepGradientContext::shadeSpan16(int x, int y, uint16_t*
 #if SK_SUPPORT_GPU
 
 #include "SkGr.h"
-#include "effects/GrExtractAlphaFragmentProcessor.h"
 #include "gl/builders/GrGLProgramBuilder.h"
 
 class GrGLSweepGradient : public GrGLGradientEffect {
@@ -292,7 +291,7 @@ const GrFragmentProcessor* SkSweepGradient::asFragmentProcessor(
 
     SkAutoTUnref<const GrFragmentProcessor> inner(
         GrSweepGradient::Create(context, procDataManager, *this, matrix));
-    return GrExtractAlphaFragmentProcessor::Create(inner);
+    return MulFragmentProcesorOuputByInputAlpha(inner);
 }
 
 #endif