Check XpFactory equality in DrawState

include/gpu/effects/GrPorterDuffXferProcessor.h

 /*
  * 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 GrPorterDuffXferProcessor_DEFINED
 #define GrPorterDuffXferProcessor_DEFINED
 
@@ skipping 50 matching lines @@
 
     static GrXPFactory* Create(GrBlendCoeff src, GrBlendCoeff dst) {
         return SkNEW_ARGS(GrPorterDuffXPFactory, (src, dst));
     }
 
     const GrXferProcessor* createXferProcessor() const SK_OVERRIDE;
 
     bool supportsRGBCoverage(GrColor knownColor, uint32_t knownColorFlags) const SK_OVERRIDE;
 
 private:
-    GrPorterDuffXPFactory(GrBlendCoeff src, GrBlendCoeff dst)
-        : fSrc(src), fDst(dst) {}
+    GrPorterDuffXPFactory(GrBlendCoeff src, GrBlendCoeff dst); 
+
+    bool onIsEqual(const GrXPFactory& xpfBase) const SK_OVERRIDE {
+        const GrPorterDuffXPFactory& xpf = xpfBase.cast<GrPorterDuffXPFactory>();
+        return (fSrc == xpf.fSrc && fDst == xpf.fDst);
+    }
 
     GrBlendCoeff fSrc;
     GrBlendCoeff fDst;
 
     typedef GrXPFactory INHERITED;
 };
 
 #endif