Enable use_once_callback on mojom GN rule by default

device/vr/BUILD.gn

 # Copyright 2016 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("features/features.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
 
 if (is_android) {
   import("//build/config/android/rules.gni")  # For generate_jni().
 }
@@ skipping 111 matching lines @@
   ]
 
   public_deps = [
     "//gpu/ipc/common:interfaces",
     "//mojo/common:common_custom_types",
   ]
 
   export_class_attribute = "DEVICE_VR_EXPORT"
   export_define = "DEVICE_VR_IMPLEMENTATION=1"
   export_header = "device/vr/vr_export.h"
+
+  # TODO(crbug.com/714018): Convert the implementation to use OnceCallback.
+  use_once_callback = false
 }