Create GrGLSLVaryingHandler class for program building

src/gpu/glsl/GrGLSLGeometryShaderBuilder.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 GrGLSLGeometryShaderBuilder_DEFINED
 #define GrGLSLGeometryShaderBuilder_DEFINED
 
 #include "GrGLSLShaderBuilder.h"
 
 class GrGLSLVarying;
 
 class GrGLSLGeometryBuilder : public GrGLSLShaderBuilder {
 public:
     GrGLSLGeometryBuilder(GrGLSLProgramBuilder* program);
 
 private:
-    /*
-     * an internal call for GrGLFullProgramBuilder to add varyings
-     */
-    void addVarying(const char* name, GrSLPrecision precision, GrGLSLVarying*);
-
-    void onFinalize() override {}
+    void onFinalize() override;
 
     friend class GrGLProgramBuilder;
 
     typedef GrGLSLShaderBuilder INHERITED;
 };
 
 #endif