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..cfbbffdbd9d7ac99ef6e718d48821516c7e05a2f 100644
--- a/include/gpu/GrPaint.h
+++ b/include/gpu/GrPaint.h
@@ -70,7 +70,7 @@ public:
         fXPFactory.reset(GrPorterDuffXPFactory::Create(mode));
     }
 
-    void setPorterDuffXPFactory(GrBlendCoeff src, GrBlendCoeff dst) {
+    void setPorterDuffXPFactory(SkXfermode::Coeff src, SkXfermode::Coeff dst) {
         fXPFactory.reset(GrPorterDuffXPFactory::Create(src, dst));
     }