make egl_native.cc compile on OSX

No idea why this doesn't work sometimes. It works for me but
not for others. Maybe which verison of XCode?

BUG=83382


Review URL: https://chromiumcodereview.appspot.com/10826152

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@150029 0039d316-1c4b-4281-b951-d872f2087c98

gpu/gles2_conform_support/native/egl_native.cc

@@ -23,14 +23,14 @@ void GTFNativeDestroyPixmap(EGLNativeDisplayType nativeDisplay,
 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) {