Add support of vrdisplayconnect and vrdisplaydisconnect event

device/vr/android/gvr/gvr_device.cc

Index: device/vr/android/gvr/gvr_device.cc
diff --git a/device/vr/android/gvr/gvr_device.cc b/device/vr/android/gvr/gvr_device.cc
index f3eebd59c73aa5acbea725c52c065e584428d15d..e952937dacf6d01e92e04182c2063831ce44951f 100644
--- a/device/vr/android/gvr/gvr_device.cc
+++ b/device/vr/android/gvr/gvr_device.cc
@@ -24,7 +24,10 @@ static const uint64_t kPredictionTimeWithoutVsyncNanos = 50000000;
 }  // namespace
 
 GvrDevice::GvrDevice(VRDeviceProvider* provider, GvrDelegate* delegate)
-    : VRDevice(provider), delegate_(delegate) {}
+    : VRDevice(provider),
+      delegate_(delegate),
+      isConnected_(false),
+      isConnectionStatusChanged_(false) {}
 
 GvrDevice::~GvrDevice() {}
 
@@ -163,4 +166,7 @@ void GvrDevice::UpdateLayerBounds(VRLayerBoundsPtr leftBounds,
                                       rightBounds->width, rightBounds->height);
 }
 
+// It will poll status from device and resolve it.
+void GvrDevice::PollEvents() {}
+
 }  // namespace device