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

ui/ozone/ozone.gyp

Index: ui/ozone/ozone.gyp
diff --git a/ui/ozone/ozone.gyp b/ui/ozone/ozone.gyp
index 5f64c5f265e2787f2a9e3de5926f397907b750ea..1f4bfc4160f4eb0a366f98979bd3d01e56f70395 100644
--- a/ui/ozone/ozone.gyp
+++ b/ui/ozone/ozone.gyp
@@ -16,6 +16,13 @@
     'internal_ozone_platforms': [],
     'internal_ozone_platform_deps': [],
     'internal_ozone_platform_unittest_deps': [],
+
+    # 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': [
     {
@@ -198,6 +205,19 @@
         '<@(internal_ozone_platform_unittest_deps)',
       ],
     },
+    {
+      'target_name': 'vgem_map',
+      'type': 'none',
+      'conditions': [
+        ['use_vgem_map==1', {
+          'direct_dependent_settings': {
+            'defines': [
+              'USE_VGEM_MAP',
+            ],
+          },
+        }],
+      ],
+    },
   ],
   'conditions': [
     ['<(ozone_platform_caca) == 1', {