Add third_party/khronos to GN configs in ozone gbm

ui/ozone/platform/drm/BUILD.gn

 # 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.
 
 import("//build/config/linux/pkg_config.gni")
 import("//ui/ozone/ozone.gni")
 
 declare_args() {
   use_mesa_platform_null = false
   use_drm_atomic = false
@@ skipping 165 matching lines @@
     ]
 
     deps = [
       ":drm_common",
       "//base",
       "//skia",
       "//ui/events/ozone:events_ozone_evdev",
       "//ui/events/ozone:events_ozone_layout",
     ]
 
-    public_configs = [ ":libgbm" ]
+    public_configs = [
+      ":libgbm",
+      "//third_party/khronos:khronos_headers",
+    ]
 
     if (use_mesa_platform_null) {
       defines += [ "USE_MESA_PLATFORM_NULL" ]
     }
   }
 }