Move GrGLInterface function pointers into a nested struct

src/gpu/gl/GrGLUtil.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "GrGLUtil.h"
 #include "SkMatrix.h"
 #include <stdio.h>
 
 void GrGLClearErr(const GrGLInterface* gl) {
-    while (GR_GL_NO_ERROR != gl->fGetError()) {}
+    while (GR_GL_NO_ERROR != gl->fFunctions.fGetError()) {}
 }
 
 namespace {
 const char *get_error_string(uint32_t err) {
     switch (err) {
     case GR_GL_NO_ERROR:
         return "";
     case GR_GL_INVALID_ENUM:
         return "Invalid Enum";
     case GR_GL_INVALID_VALUE:
@@ skipping 262 matching lines @@
     dest[9]  = 0;
     dest[10] = 1;
     dest[11] = 0;
 
     // Col 3
     dest[12] = SkScalarToFloat(src[SkMatrix::kMTransX]);
     dest[13] = SkScalarToFloat(src[SkMatrix::kMTransY]);
     dest[14] = 0;
     dest[15] = SkScalarToFloat(src[SkMatrix::kMPersp2]);
 }