Add support of vrdisplayconnect and vrdisplaydisconnect event

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 c6896be2eca531b52ad965b7fc72d715408b0ab6..f388278cf956002cf65aca1fdb116e508c02af5a 100644
--- a/device/vr/vr_device_provider.h
+++ b/device/vr/vr_device_provider.h
@@ -9,6 +9,7 @@
 
 namespace device {
 
+class VRClientDispatcher;
 class VRDevice;
 
 class VRDeviceProvider {
@@ -22,6 +23,8 @@ class VRDeviceProvider {
   virtual void Initialize() = 0;
 
   virtual void PollEvents() {}
+
+  virtual void SetClient(VRClientDispatcher* client) {}
 };
 
 }  // namespace device