Add event listening function to openvr device

device/vr/openvr/openvr_device.h

Index: device/vr/openvr/openvr_device.h
diff --git a/device/vr/openvr/openvr_device.h b/device/vr/openvr/openvr_device.h
index 136f5667fd226c7e650e489d3e7491d0fbee37cc..08c0018c9fb5036e9505b9f5358ba26ff9d6c593 100644
--- a/device/vr/openvr/openvr_device.h
+++ b/device/vr/openvr/openvr_device.h
@@ -18,6 +18,8 @@ namespace device {
 
 class OpenVRDevice : public VRDevice {
  public:
+  enum VREvent { CONNECTED = 0, DISCONNECTED = 1, CHANGED = 2 };
+
   OpenVRDevice();
   ~OpenVRDevice() override;
 
@@ -39,16 +41,28 @@ class OpenVRDevice : public VRDevice {
                          int16_t source_height) override;
   void GetVRVSyncProvider(mojom::VRVSyncProviderRequest request) override;
 
+  void OnPollingEvent(OpenVRDevice::VREvent event);
+
  private:
   class OpenVRRenderLoop : public base::SimpleThread,
                            device::mojom::VRVSyncProvider {
    public:
     OpenVRRenderLoop(vr::IVRSystem* vr);
 
+    void RegistPollingEventCallback(
+        const base::Callback<void(OpenVRDevice::VREvent)>& onPollingVREvent);
+
+    void UnregistPollingEventCallback();
+
     void Bind(mojom::VRVSyncProviderRequest request);
 
     mojom::VRPosePtr getPose();
 
+    vr::IVRSystem* GetVRSystem();
+
+    // OpenVR need invoke pollNextEvent to query system event.
+    void PollEvents();
+
    private:
     void Run() override;
 
@@ -56,6 +70,7 @@ class OpenVRDevice : public VRDevice {
                       callback) override;
 
     scoped_refptr<base::SingleThreadTaskRunner> main_thread_task_runner_;
+    base::Callback<void(OpenVRDevice::VREvent)> on_polling_event_;
     vr::IVRSystem* vr_system_;
     mojo::Binding<device::mojom::VRVSyncProvider> binding_;
   };
@@ -68,6 +83,8 @@ class OpenVRDevice : public VRDevice {
 
   mojom::VRSubmitFrameClientPtr submit_client_;
 
+  base::WeakPtrFactory<OpenVRDevice> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(OpenVRDevice);
 };