Make XPFragmentBuilder only Builder with access to DstCopy.

src/gpu/gl/builders/GrGLProgramBuilder.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 GrGLProgramBuilder_DEFINED
 #define GrGLProgramBuilder_DEFINED
 
@@ skipping 137 matching lines @@
     /*
      * This call can be used by GP to pass an attribute through all shaders directly to 'output' in
      * the fragment shader.  Though this call effects both the vertex shader and fragment shader,
      * it expects 'output' to be defined in the fragment shader before this call is made.
      * TODO it might be nicer behavior to have a flag to declare output inside this call
      */
     virtual void addPassThroughAttribute(const GrGeometryProcessor::Attribute*,
                                          const char* output) = 0;
 
     // TODO rename getFragmentBuilder
-    virtual GrGLGPFragmentBuilder* getFragmentShaderBuilder() = 0;
+    virtual GrGLFragmentBuilder* getFragmentShaderBuilder() = 0;
     virtual GrGLVertexBuilder* getVertexShaderBuilder() = 0;
 
     /*
      * *NOTE* NO MEMBERS ALLOWED, MULTIPLE INHERITANCE
      */
 };
 
 /* a specializations for FPs. Lets the user add uniforms and FS code */
 class GrGLFPBuilder : public virtual GrGLUniformBuilder {
 public:
-    virtual GrGLFPFragmentBuilder* getFragmentShaderBuilder() = 0;
+    virtual GrGLFragmentBuilder* getFragmentShaderBuilder() = 0;
 
     /*
      * *NOTE* NO MEMBERS ALLOWED, MULTIPLE INHERITANCE
      */
 };
 
 /* a specializations for XPs. Lets the user add uniforms and FS code */
 class GrGLXPBuilder : public virtual GrGLUniformBuilder {
 public:
-    virtual GrGLFPFragmentBuilder* getFragmentShaderBuilder() = 0;
+    virtual GrGLXPFragmentBuilder* getFragmentShaderBuilder() = 0;
 
     /*
      * *NOTE* NO MEMBERS ALLOWED, MULTIPLE INHERITANCE
      */
 };
 
 /**
  * The below struct represent processors installed in programs.
  */
 template <class Proc>
@@ skipping 51 matching lines @@
     }
 
     const char* getUniformCStr(UniformHandle u) const override {
         return this->getUniformVariable(u).c_str();
     }
 
     const GrGLContextInfo& ctxInfo() const override;
 
     GrGLGpu* gpu() const override { return fGpu; }
 
-    GrGLFPFragmentBuilder* getFragmentShaderBuilder() override { return &fFS; }
+    GrGLXPFragmentBuilder* getFragmentShaderBuilder() override { return &fFS; }
     GrGLVertexBuilder* getVertexShaderBuilder() override { return &fVS; }
 
     void addVarying(
             const char* name,
             GrGLVarying*,
             GrSLPrecision fsPrecision = kDefault_GrSLPrecision) override;
 
     void addPassThroughAttribute(const GrPrimitiveProcessor::Attribute*,
                                  const char* output) override;
 
@@ skipping 129 matching lines @@
     UniformInfoArray fUniforms;
     GrGLPrimitiveProcessor::TransformsIn fCoordTransforms;
     GrGLPrimitiveProcessor::TransformsOut fOutCoords;
 
     friend class GrGLShaderBuilder;
     friend class GrGLVertexBuilder;
     friend class GrGLFragmentShaderBuilder;
     friend class GrGLGeometryBuilder;
 };
 #endif