Implement support for KHR_blend_equation_advanced

include/core/SkXfermode.h

Index: include/core/SkXfermode.h
diff --git a/include/core/SkXfermode.h b/include/core/SkXfermode.h
index 1dd01a2e1d7f0cf526e3c9f078f3ac7aebdd58de..745df2ca80e47795b6cbe0f193bf32c8babdf3da 100644
--- a/include/core/SkXfermode.h
+++ b/include/core/SkXfermode.h
@@ -13,6 +13,7 @@
 #include "SkFlattenable.h"
 #include "SkColor.h"
 
+class GrContext;
 class GrFragmentProcessor;
 class GrTexture;
 class GrXPFactory;
@@ -217,13 +218,13 @@ public:
         will install it and own a ref to it. Since the xfermode may or may not assign *xpf, the
         caller should set *xpf to NULL beforehand. XferProcessors cannot use a background texture.
      */
-    virtual bool asXPFactory(GrXPFactory** xpf) const;
+    virtual bool asXPFactory(const GrContext*, GrXPFactory** xpf) const;
 
     /** Returns true if the xfermode can be expressed as an xfer processor factory (xpFactory).
         This helper calls the asXPFactory() virtual. If the xfermode is NULL, it is treated as
         kSrcOver_Mode. It is legal to call this with xpf param NULL to simply test the return value.
      */
-    static bool AsXPFactory(SkXfermode*, GrXPFactory**);
+    static bool AsXPFactory(SkXfermode*, const GrContext*, GrXPFactory**);
 
     SK_TO_STRING_PUREVIRT()
     SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()