Don't create a GXPFactory when blend is SrcOver

src/core/SkXfermode.cpp

Index: src/core/SkXfermode.cpp
diff --git a/src/core/SkXfermode.cpp b/src/core/SkXfermode.cpp
index 9083814d1a66b97a00e05436f0dd8e7c61ab44ee..79de322c2daceb95dce39bfc304776556e5ade70 100644
--- a/src/core/SkXfermode.cpp
+++ b/src/core/SkXfermode.cpp
@@ -660,26 +660,6 @@ bool SkXfermode::asXPFactory(GrXPFactory**) const {
     return false;
 }
 
-
-#if SK_SUPPORT_GPU
-#include "effects/GrPorterDuffXferProcessor.h"
-
-bool SkXfermode::AsXPFactory(SkXfermode* xfermode, GrXPFactory** xpf) {
-    if (nullptr == xfermode) {
-        if (xpf) {
-            *xpf = GrPorterDuffXPFactory::Create(kSrcOver_Mode);
-        }
-        return true;
-    } else {
-        return xfermode->asXPFactory(xpf);
-    }
-}
-#else
-bool SkXfermode::AsXPFactory(SkXfermode* xfermode, GrXPFactory** xpf) {
-    return false;
-}
-#endif
-
 SkPMColor SkXfermode::xferColor(SkPMColor src, SkPMColor dst) const{
     // no-op. subclasses should override this
     return dst;
@@ -920,6 +900,7 @@ void SkProcCoeffXfermode::xferA8(SkAlpha* SK_RESTRICT dst,
 
 #if SK_SUPPORT_GPU
 #include "effects/GrCustomXfermode.h"
+#include "effects/GrPorterDuffXferProcessor.h"
 #include "effects/GrXfermodeFragmentProcessor.h"
 
 bool SkProcCoeffXfermode::asFragmentProcessor(const GrFragmentProcessor** fp,