Move GrGLInterface function pointers into a nested struct

src/gpu/gl/GrGLContext.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrGLContext.h"
 
 ////////////////////////////////////////////////////////////////////////////////
 
 GrGLContextInfo& GrGLContextInfo::operator= (const GrGLContextInfo& that) {
     fInterface.reset(SkSafeRef(that.fInterface.get()));
     fGLVersion      = that.fGLVersion;
     fGLSLGeneration = that.fGLSLGeneration;
     fVendor         = that.fVendor;
     fRenderer       = that.fRenderer;
     fIsMesa         = that.fIsMesa;
     fIsChromium     = that.fIsChromium;
     *fGLCaps        = *that.fGLCaps.get();
     return *this;
 }
 
 bool GrGLContextInfo::initialize(const GrGLInterface* interface) {
     this->reset();
     // We haven't validated the GrGLInterface yet, so check for GetString
     // function pointer
-    if (interface->fGetString) {
+    if (interface->fFunctions.fGetString) {
         const GrGLubyte* verUByte;
         GR_GL_CALL_RET(interface, verUByte, GetString(GR_GL_VERSION));
         const char* ver = reinterpret_cast<const char*>(verUByte);
 
         const GrGLubyte* rendererUByte;
         GR_GL_CALL_RET(interface, rendererUByte, GetString(GR_GL_RENDERER));
         const char* renderer = reinterpret_cast<const char*>(rendererUByte);
 
         if (interface->validate()) {
 
@@ skipping 27 matching lines @@
 void GrGLContextInfo::reset() {
     fInterface.reset(NULL);
     fGLVersion = GR_GL_VER(0, 0);
     fGLSLGeneration = static_cast<GrGLSLGeneration>(0);
     fVendor = kOther_GrGLVendor;
     fRenderer = kOther_GrGLRenderer;
     fIsMesa = false;
     fIsChromium = false;
     fGLCaps->reset();
 }