Implement support for KHR_blend_equation_advanced

src/effects/SkArithmeticMode.cpp

Index: src/effects/SkArithmeticMode.cpp
diff --git a/src/effects/SkArithmeticMode.cpp b/src/effects/SkArithmeticMode.cpp
index 4914c696ee57eb5267a5d4f3a353195077ee1a6b..0d10b9d24416b12be3529f3142d80a1869f1164a 100644
--- a/src/effects/SkArithmeticMode.cpp
+++ b/src/effects/SkArithmeticMode.cpp
@@ -33,7 +33,7 @@ public:
 #if SK_SUPPORT_GPU
     bool asFragmentProcessor(GrFragmentProcessor**, GrTexture* background) const override;
 
-    bool asXPFactory(GrXPFactory**) const override;
+    bool asXPFactory(const GrContext*, GrXPFactory**) const override;
 #endif
 
 private:
@@ -247,7 +247,7 @@ bool SkArithmeticMode_scalar::asFragmentProcessor(GrFragmentProcessor** fp,
     return true;
 }
 
-bool SkArithmeticMode_scalar::asXPFactory(GrXPFactory** xpf) const {
+bool SkArithmeticMode_scalar::asXPFactory(const GrContext*, GrXPFactory** xpf) const {
     if (xpf) {
         *xpf = GrArithmeticXPFactory::Create(SkScalarToFloat(fK[0]),
                                              SkScalarToFloat(fK[1]),