Migrate vr to use inlined tracing

Source/modules/vr/PositionSensorVRDevice.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/PositionSensorVRDevice.h"
 
 #include "public/platform/Platform.h"
 
 namespace blink {
@@ skipping 12 matching lines @@
 VRPositionState* PositionSensorVRDevice::getImmediateState()
 {
     return hardwareUnit()->getPositionState();
 }
 
 void PositionSensorVRDevice::resetSensor()
 {
     blink::Platform::current()->resetVRSensor(index());
 }
 
-void PositionSensorVRDevice::trace(Visitor* visitor)
+DEFINE_TRACE(PositionSensorVRDevice)
 {
     VRDevice::trace(visitor);
 }
 
 } // namespace blink