Add XferProcessor factory in GrPaint and GrDrawState.

src/gpu/effects/GrDefaultXferProcessor.h

Index: src/gpu/effects/GrDefaultXferProcessor.h
diff --git a/src/gpu/effects/GrDefaultXferProcessor.h b/src/gpu/effects/GrDefaultXferProcessor.h
new file mode 100644
index 0000000000000000000000000000000000000000..fe3f20982f185f7e5e3a20650d0a5feec06127c5
--- /dev/null
+++ b/src/gpu/effects/GrDefaultXferProcessor.h
@@ -0,0 +1,27 @@
+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef GrDefaultXferProcessor_DEFINED
+#define GrDefaultXferProcessor_DEFINED
+
+#include "GrPorterDuffXferProcessor.h"
+
+class GrDefaultXPFactory : public GrPorterDuffXPFactory {

[bsalomon, 2014/12/01 19:24:40]

Does it make sense to have this at all?

+public:
+    static const GrXPFactory* Create() {
+        GR_CREATE_STATIC_XP_FACTORY(gDefaultXPFactory, GrDefaultXPFactory, ());
+        return SkRef(gDefaultXPFactory);
+    }
+
+private:
+    GrDefaultXPFactory() : INHERITED(SkXfermode::kOne_Coeff, SkXfermode::kZero_Coeff) {}
+
+    typedef GrPorterDuffXPFactory INHERITED;
+};
+
+#endif
+