Add support of vrdisplayconnect and vrdisplaydisconnect event

device/vr/android/gvr/gvr_device_provider.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_PROVIDER_H
 #define DEVICE_VR_ANDROID_GVR_DEVICE_PROVIDER_H
 
 #include <memory>
 
 #include "base/macros.h"
 #include "device/vr/android/gvr/gvr_delegate.h"
 #include "device/vr/vr_device.h"
 #include "device/vr/vr_device_provider.h"
 
 namespace device {
 
+class VRClientDispatcher;
 class GvrDeviceProviderDelegate;
 
 class GvrDeviceProvider : public VRDeviceProvider, public GvrDelegateClient {
  public:
   GvrDeviceProvider();
   ~GvrDeviceProvider() override;
 
   void GetDevices(std::vector<VRDevice*>* devices) override;
   void Initialize() override;
 
   // 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_;
 
   DISALLOW_COPY_AND_ASSIGN(GvrDeviceProvider);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_VR_ANDROID_GVR_DEVICE_PROVIDER_H