Add in shader blending for CoverageSetOp XP

src/gpu/glsl/GrGLSLXferProcessor.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 GrGLSLXferProcessor_DEFINED
 #define GrGLSLXferProcessor_DEFINED
 
@@ skipping 67 matching lines @@
     }
 
     /**
      * Called by emitCode() when the XP will perform a dst read. This method only needs to supply
      * the blending logic. The base class applies coverage. A subclass only needs to implement this
      * method if it can construct a GrXferProcessor that reads the dst color.
      */
     virtual void emitBlendCodeForDstRead(GrGLSLXPBuilder*,
                                          GrGLSLXPFragmentBuilder*,
                                          const char* srcColor,
+                                         const char* srcCoverage,
                                          const char* dstColor,
                                          const char* outColor,
+                                         const char* outColorSecondary,
                                          const GrXferProcessor&) {
         SkFAIL("emitBlendCodeForDstRead not implemented.");
     }
 
     virtual void onSetData(const GrGLSLProgramDataManager&, const GrXferProcessor&) = 0;
 
     GrGLSLProgramDataManager::UniformHandle fDstTopLeftUni;
     GrGLSLProgramDataManager::UniformHandle fDstScaleUni;
 };
 #endif