Use SkXfermode as public facing enum for GrPorterDuffXP

src/gpu/GrPipelineBuilder.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrPipelineBuilder_DEFINED
 #define GrPipelineBuilder_DEFINED
 
@@ skipping 100 matching lines @@
      */
     const GrXPFactory* setXPFactory(const GrXPFactory* xpFactory) {
         fXPFactory.reset(SkRef(xpFactory));
         return xpFactory;
     }
 
     void setPorterDuffXPFactory(SkXfermode::Mode mode) {
         fXPFactory.reset(GrPorterDuffXPFactory::Create(mode));
     }
 
-    void setPorterDuffXPFactory(GrBlendCoeff src, GrBlendCoeff dst) {
-        fXPFactory.reset(GrPorterDuffXPFactory::Create(src, dst));
-    }
-
     void setCoverageSetOpXPFactory(SkRegion::Op regionOp, bool invertCoverage = false) {
         fXPFactory.reset(GrCoverageSetOpXPFactory::Create(regionOp, invertCoverage));
     }
 
     void setDisableColorXPFactory() {
         fXPFactory.reset(GrDisableColorXPFactory::Create());
     }
 
     const GrFragmentProcessor* addColorProcessor(const GrFragmentProcessor* effect) {
         SkASSERT(effect);
@@ skipping 326 matching lines @@
     mutable GrProcOptInfo fCoverageProcInfo;
     mutable bool fColorProcInfoValid;
     mutable bool fCoverageProcInfoValid;
     mutable GrColor fColorCache;
     mutable GrColor fCoverageCache;
 
     friend class GrPipeline;
 };
 
 #endif