Use SkXfermode as public facing enum for GrPorterDuffXP

include/gpu/GrPaint.h

Index: include/gpu/GrPaint.h
diff --git a/include/gpu/GrPaint.h b/include/gpu/GrPaint.h
index 64b51d2c650703d5f6636042e4892ac5731dff3f..bf2969311507495958c76e0ae4750e0c195e352a 100644
--- a/include/gpu/GrPaint.h
+++ b/include/gpu/GrPaint.h
@@ -15,6 +15,7 @@
 #include "GrXferProcessor.h"
 #include "effects/GrPorterDuffXferProcessor.h"
 
+#include "SkRegion.h"
 #include "SkXfermode.h"
 
 /**
@@ -70,9 +71,7 @@ public:
         fXPFactory.reset(GrPorterDuffXPFactory::Create(mode));
     }
 
-    void setPorterDuffXPFactory(GrBlendCoeff src, GrBlendCoeff dst) {
-        fXPFactory.reset(GrPorterDuffXPFactory::Create(src, dst));
-    }
+    void setCoverageSetOpXPFactory(SkRegion::Op regionOp, bool invertCoverage = false); 
 
     /**
      * Appends an additional color processor to the color computation.