Oilpan: have Navigator and its supplements be on the heap by default.

Source/modules/vr/VRGetDevicesCallback.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 VRGetDevicesCallback_h
 #define VRGetDevicesCallback_h
 
 #include "platform/heap/Handle.h"
 #include "public/platform/WebVRClient.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefPtr.h"
 
 namespace blink {
 
 class VRHardwareUnitCollection;
 class ScriptPromiseResolver;
 class WebVRClient;
 
 class VRGetDevicesCallback final : public WebVRGetDevicesCallback {
 public:
     VRGetDevicesCallback(PassRefPtrWillBeRawPtr<ScriptPromiseResolver>, VRHardwareUnitCollection*);
     ~VRGetDevicesCallback() override;
 
     void onSuccess(WebVector<blink::WebVRDevice>*) override;
     void onError() override;
 
 private:
     RefPtrWillBePersistent<ScriptPromiseResolver> m_resolver;
-    RefPtrWillBePersistent<VRHardwareUnitCollection> m_hardwareUnits;
+    Persistent<VRHardwareUnitCollection> m_hardwareUnits;
 };
 
 } // namespace blink
 
 #endif // VRGetDevicesCallback_h