Implement WebVR presentation pausing for VR Shell Menu Mode

device/vr/vr_device_provider.h

Index: device/vr/vr_device_provider.h
diff --git a/device/vr/vr_device_provider.h b/device/vr/vr_device_provider.h
index f388278cf956002cf65aca1fdb116e508c02af5a..05421117ff14521e5cc42a47dd34ab8bf887b163 100644
--- a/device/vr/vr_device_provider.h
+++ b/device/vr/vr_device_provider.h
@@ -7,15 +7,16 @@
 
 #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;
 
@@ -25,6 +26,10 @@ class VRDeviceProvider {
   virtual void PollEvents() {}
 
   virtual void SetClient(VRClientDispatcher* client) {}
+
+ protected:
+  friend class base::RefCountedThreadSafe<VRDeviceProvider>;
+  virtual ~VRDeviceProvider() {}
 };
 
 }  // namespace device