Remove hasMixedSamples() from GrPipelineBuilder

src/gpu/effects/GrDisableColorXP.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 GrDisableColorXP_DEFINED
 #define GrDisableColorXP_DEFINED
 
@@ skipping 13 matching lines @@
     }
 
 private:
     GrDisableColorXPFactory();
 
     GrXferProcessor* onCreateXferProcessor(const GrCaps& caps,
                                            const GrPipelineOptimizations& optimizations,
                                            bool hasMixedSamples,
                                            const DstTexture* dstTexture) const override;
 
-    bool onWillReadDstColor(const GrCaps& caps,
-                            const GrPipelineOptimizations& optimizations,
-                            bool hasMixedSamples) const override {
+    bool onWillReadDstColor(const GrCaps&, const GrPipelineOptimizations&) const override {
         return false;
     }
 
     bool onIsEqual(const GrXPFactory& xpfBase) const override {
         return true;
     }
 
     GR_DECLARE_XP_FACTORY_TEST;
 
     typedef GrXPFactory INHERITED;
 };
 
 #endif