Notify VRDeviceProviders when there are pages listening for vrdisplayactivate

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 0e1d879393e1b86c8f3e36eb63f149f80e4f641b..8c162f286f27e663da52333813004eb122cd350a 100644
--- a/device/vr/android/gvr/gvr_device_provider.h
+++ b/device/vr/android/gvr/gvr_device_provider.h
@@ -29,6 +29,8 @@ class DEVICE_VR_EXPORT GvrDeviceProvider : public VRDeviceProvider {
   void GetDevices(std::vector<VRDevice*>* devices) override;
   void Initialize() override;
 
+  void SetListeningForActivate(bool listening) override;
+
   // Called from GvrDevice.
   void RequestPresent(const base::Callback<void(bool)>& callback);
   void ExitPresent();