Implement WebVR presentation pausing for VR Shell Menu Mode

device/vr/vr_device_provider.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 DEVICE_VR_VR_DEVICE_PROVIDER_H
 #define DEVICE_VR_VR_DEVICE_PROVIDER_H
 
 #include <vector>
 
+#include "base/memory/ref_counted.h"
+
 namespace device {
 
 class VRClientDispatcher;
 class VRDevice;
 
-class VRDeviceProvider {
+class VRDeviceProvider : public base::RefCountedThreadSafe<VRDeviceProvider> {
  public:
   VRDeviceProvider() {}
-  virtual ~VRDeviceProvider() {}
 
   virtual void GetDevices(std::vector<VRDevice*>* devices) = 0;
 
   // If the VR API requires initialization that should happen here.
   virtual void Initialize() = 0;
 
   virtual void PollEvents() {}
 
   virtual void SetClient(VRClientDispatcher* client) {}
+
+ protected:
+  friend class base::RefCountedThreadSafe<VRDeviceProvider>;
+  virtual ~VRDeviceProvider() {}
 };
 
 }  // namespace device
 
 #endif  // DEVICE_VR_VR_DEVICE_PROVIDER_H