Migrate vr to use inlined tracing

Source/modules/vr/VRHardwareUnit.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/VRHardwareUnit.h"
 
 #include "modules/vr/HMDVRDevice.h"
 #include "modules/vr/PositionSensorVRDevice.h"
 #include "modules/vr/VRDevice.h"
@@ skipping 75 matching lines @@
     case VREyeLeft:
         return new VRFieldOfView(*m_currentFOVLeft);
     case VREyeRight:
         return new VRFieldOfView(*m_currentFOVRight);
     default:
         ASSERT_NOT_REACHED();
         return nullptr;
     }
 }
 
-void VRHardwareUnit::trace(Visitor* visitor)
+DEFINE_TRACE(VRHardwareUnit)
 {
     visitor->trace(m_positionState);
     visitor->trace(m_currentFOVLeft);
     visitor->trace(m_currentFOVRight);
     visitor->trace(m_hmd);
     visitor->trace(m_positionSensor);
 }
 
 } // namespace blink