make egl_native.cc compile on OSX

gpu/gles2_conform_support/native/egl_native.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 extern "C" {
 #if defined(GLES2_CONFORM_SUPPORT_ONLY)
 #include "gpu/gles2_conform_support/gtf/gtf_stubs.h"
 #else
 #include "third_party/gles2_conform/GTF_ES/glsl/GTF/Source/eglNative.h"
 #endif
 
 GTFbool GTFNativeCreatePixmap(EGLNativeDisplayType nativeDisplay,
                               EGLDisplay eglDisplay, EGLConfig eglConfig,
                               const char *title, int width, int height,
                               EGLNativePixmapType *pNativePixmap) {
   return GTFtrue;
 }
 
 void GTFNativeDestroyPixmap(EGLNativeDisplayType nativeDisplay,
                             EGLNativePixmapType nativePixmap) {
 }
 
 EGLImageKHR GTFCreateEGLImageExternal(
     int width, int height, int format,
     float r, float g, float b, float a, void** resource) {
-  return (EGLImageKHR)NULL;
+  return (EGLImageKHR)0;
 }
 
 void GTFDestroyEGLImageExternal(EGLImageKHR image, void* resource) {
 }
 
 const int* GTFQueryFormatsEGLImageExternal(void) {
-  return NULL;
+  return 0;
 }
 
 GTFbool GTFIsAlphaFormatEGLImageExternal(int format) {
   return GTFfalse;
 }
 
 }  // extern "C"