Add support of vrdisplayconnect and vrdisplaydisconnect event

device/vr/android/gvr/gvr_device.h

 // Copyright 2016 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_ANDROID_GVR_DEVICE_H
 #define DEVICE_VR_ANDROID_GVR_DEVICE_H
 
 #include "base/macros.h"
 #include "device/vr/vr_device.h"
 
 namespace gvr {
 class GvrApi;
 }  // namespace gvr
 
 namespace device {
 
 class GvrDevice : public VRDevice {
  public:
   GvrDevice(VRDeviceProvider* provider, gvr::GvrApi* gvr_api);
   ~GvrDevice() override;
 
   // VRDevice
   VRDisplayPtr GetVRDevice() override;
   VRPosePtr GetPose() override;
   void ResetPose() override;
 
+  virtual void PollEvents() override;
+
  private:
   gvr::GvrApi* gvr_api_;
 
+  bool isConnected;
+
   DISALLOW_COPY_AND_ASSIGN(GvrDevice);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_VR_ANDROID_GVR_DEVICE_H