Use SkXfermode as public facing enum for GrPorterDuffXP

src/gpu/GrPaint.cpp

Index: src/gpu/GrPaint.cpp
diff --git a/src/gpu/GrPaint.cpp b/src/gpu/GrPaint.cpp
index d35b41feb31c8ff9ec512c18347ca2705204d232..c9cebad9d8077e9f91f135a6fb3ef93c0ce75d40 100644
--- a/src/gpu/GrPaint.cpp
+++ b/src/gpu/GrPaint.cpp
@@ -9,6 +9,7 @@
 #include "GrPaint.h"
 
 #include "GrProcOptInfo.h"
+#include "effects/GrCoverageSetOpXP.h"
 #include "effects/GrPorterDuffXferProcessor.h"
 #include "effects/GrSimpleTextureEffect.h"
 
@@ -18,6 +19,10 @@ GrPaint::GrPaint()
     , fColor(GrColor_WHITE) {
 }
 
+void GrPaint::setCoverageSetOpXPFactory(SkRegion::Op regionOp, bool invertCoverage) {
+    fXPFactory.reset(GrCoverageSetOpXPFactory::Create(regionOp, invertCoverage));
+}
+
 void GrPaint::addColorTextureProcessor(GrTexture* texture, const SkMatrix& matrix) {
     this->addColorProcessor(GrSimpleTextureEffect::Create(texture, matrix))->unref();
 }