Enable WebVR origin trial experiments.

third_party/WebKit/Source/modules/vr/VRDisplayEvent.idl

 // 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.
 
 enum VRDisplayEventReason {
     "connected",
     "disconnected",
     "navigation",
     "mounted",
     "unmounted"
 };
 
 // https://w3c.github.io/webvr/#interface-vrdisplayevent
 [
-    RuntimeEnabled=WebVR,
+    OriginTrialEnabled=WebVR,
     Constructor(DOMString type, optional VRDisplayEventInit eventInitDict),
 ] interface VRDisplayEvent : Event {
     readonly attribute VRDisplay display;
     readonly attribute VRDisplayEventReason reason;
 };