Remove willReadDst from GrFragmentProcessor.

src/effects/SkArithmeticMode_gpu.h

Index: src/effects/SkArithmeticMode_gpu.h
diff --git a/src/effects/SkArithmeticMode_gpu.h b/src/effects/SkArithmeticMode_gpu.h
index 424bef6f91f57ab9c9d741c2cfd4ad70f9cfdcd9..2998eabc3b48ecdd11411941a150331845f04793 100644
--- a/src/effects/SkArithmeticMode_gpu.h
+++ b/src/effects/SkArithmeticMode_gpu.h
@@ -154,10 +154,7 @@ public:
     void getInvariantOutput(const GrProcOptInfo& colorPOI, const GrProcOptInfo& coveragePOI,
                             GrXPFactory::InvariantOutput*) const SK_OVERRIDE;
 
-    bool willReadDst(const GrProcOptInfo& colorPOI,
-                     const GrProcOptInfo& coveragePOI) const SK_OVERRIDE {
-        return true;
-    }
+    bool willReadDst() const SK_OVERRIDE { return true; }
 
 private:
     GrArithmeticXPFactory(float k1, float k2, float k3, float k4, bool enforcePMColor);