Migrate vr to use inlined tracing

Source/modules/vr/VRDevice.cpp

 // Copyright 2015 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.
 
 #include "config.h"
 #include "modules/vr/VRDevice.h"
 
 namespace blink {
 
 VRDevice::VRDevice(VRHardwareUnit* hardwareUnit)
     : m_hardwareUnit(hardwareUnit)
 {
 }
 
 void VRDevice::updateFromWebVRDevice(const WebVRDevice& device)
 {
     m_deviceId = device.deviceId;
     m_deviceName = device.deviceName;
 }
 
-void VRDevice::trace(Visitor* visitor)
+DEFINE_TRACE(VRDevice)
 {
     visitor->trace(m_hardwareUnit);
 }
 
 } // namespace blink