Make XPFragmentBuilder only Builder with access to DstCopy.

src/gpu/effects/GrConstColorProcessor.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "effects/GrConstColorProcessor.h"
 #include "gl/GrGLProcessor.h"
 #include "gl/GrGLSL.h"
 #include "gl/builders/GrGLProgramBuilder.h"
 
 class GLConstColorProcessor : public GrGLFragmentProcessor {
 public:
     GLConstColorProcessor() : fPrevColor(GrColor_ILLEGAL) {}
 
     void emitCode(GrGLFPBuilder* builder,
                   const GrFragmentProcessor& fp,
                   const char* outputColor,
                   const char* inputColor,
                   const TransformedCoordsArray& coords,
                   const TextureSamplerArray& samplers) override {
-        GrGLFPFragmentBuilder* fsBuilder = builder->getFragmentShaderBuilder();
+        GrGLFragmentBuilder* fsBuilder = builder->getFragmentShaderBuilder();
         const char* colorUni;
         fColorUniform = builder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
                                             kVec4f_GrSLType, kMedium_GrSLPrecision, "constantColor",
                                             &colorUni);
         switch (fp.cast<GrConstColorProcessor>().inputMode()) {
             case GrConstColorProcessor::kIgnore_InputMode:
                 fsBuilder->codeAppendf("%s = %s;", outputColor, colorUni);
                 break;
             case GrConstColorProcessor::kModulateRGBA_InputMode:
                 fsBuilder->codeAppendf("%s = %s * %s;", outputColor, inputColor, colorUni);
@@ skipping 90 matching lines @@
             color = 0;
             break;
         case 2:
             color = random->nextULessThan(0x100);
             color = color | (color << 8) | (color << 16) | (color << 24);
             break;
     }
     InputMode mode = static_cast<InputMode>(random->nextULessThan(kInputModeCnt));
     return GrConstColorProcessor::Create(color, mode);
 }