Add support of vrdisplayconnect and vrdisplaydisconnect event

device/vr/android/gvr/gvr_device_provider.h

Index: device/vr/android/gvr/gvr_device_provider.h
diff --git a/device/vr/android/gvr/gvr_device_provider.h b/device/vr/android/gvr/gvr_device_provider.h
index f2e9b21af815c445fcef6d89260f530e5d41e5a7..685ad384a4b1431afca62a9b44f518c8c345abde 100644
--- a/device/vr/android/gvr/gvr_device_provider.h
+++ b/device/vr/android/gvr/gvr_device_provider.h
@@ -14,6 +14,7 @@
 
 namespace device {
 
+class VRClientDispatcher;
 class GvrDeviceProviderDelegate;
 
 class GvrDeviceProvider : public VRDeviceProvider, public GvrDelegateClient {
@@ -28,6 +29,8 @@ class GvrDeviceProvider : public VRDeviceProvider, public GvrDelegateClient {
   void OnDelegateInitialized(GvrDelegate* delegate) override;
   void OnDelegateShutdown() override;
 
+  void PollEvents(VRClientDispatcher* client) override;
+
  private:
   std::unique_ptr<VRDevice> vr_device_;
   std::unique_ptr<GvrDeviceProviderDelegate> delegate_;