ozone gbm: whitelist 3 DRM ioctl code for native GpuMemoryBuffer.

ui/ozone/platform/drm/gbm.gypi

 # Copyright 2014 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.
 
 {
   'variables': {
     'internal_ozone_platform_deps': [
       'ozone_platform_gbm',
     ],
     'internal_ozone_platforms': [
       'gbm',
     ],
     'use_mesa_platform_null%': 0,
 
+    # This enables memory-mapped access to accelerated graphics buffers via the
+    # VGEM ("virtual GEM") driver. This is currently only available on Chrome OS
+    # kernels and affects code in the GBM ozone platform.
     # TODO(dshwang): remove this flag when all gbm hardware supports vgem map.
     # crbug.com/519587
     'use_vgem_map%': 0,
   },
   'targets': [
     {
       'target_name': 'ozone_platform_gbm',
       'type': 'static_library',
       'dependencies': [
         '../../base/base.gyp:base',
@@ skipping 37 matching lines @@
           'defines': ['USE_VGEM_MAP'],
           'sources': [
             'gpu/client_native_pixmap_vgem.cc',
             'gpu/client_native_pixmap_vgem.h',
           ],
         }],
       ],
     },
   ],
 }