Migrate vr to use inlined tracing

Source/modules/vr/VRHardwareUnit.h

 // 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.
 
 #ifndef VRHardwareUnit_h
 #define VRHardwareUnit_h
 
 #include "modules/vr/VRFieldOfView.h"
 #include "modules/vr/VRPositionState.h"
 #include "platform/heap/Handle.h"
@@ skipping 27 matching lines @@
     unsigned frameIndex() const { return m_frameIndex; }
 
     VRPositionState* getPositionState();
 
     void setFieldOfView(VREye, VRFieldOfView*);
     VRFieldOfView* getCurrentEyeFieldOfView(VREye) const;
 
     HMDVRDevice* hmd() const { return m_hmd; }
     PositionSensorVRDevice* positionSensor() const { return m_positionSensor; }
 
-    virtual void trace(Visitor*);
+    DECLARE_VIRTUAL_TRACE();
 
 private:
     unsigned m_index;
     String m_hardwareUnitId;
 
     unsigned m_frameIndex;
 
     Member<VRPositionState> m_positionState;
     Member<VRFieldOfView> m_currentFOVLeft;
     Member<VRFieldOfView> m_currentFOVRight;
 
     // Device types
     Member<HMDVRDevice> m_hmd;
     Member<PositionSensorVRDevice> m_positionSensor;
 };
 
 } // namespace blink
 
 #endif // VRHardwareUnit_h