Fix exiting WebVR via Android UI not fully exiting fullscreen.

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 be3d657764f9e225620d4fe22dca6cb6b5c1d545..da7b6a197796028edc823e856b4305be48d014e5 100644
--- a/device/vr/android/gvr/gvr_device.cc
+++ b/device/vr/android/gvr/gvr_device.cc
@@ -218,11 +218,10 @@ bool GvrDevice::RequestPresent(VRServiceImpl* service, bool secure_origin) {
 }
 
 void GvrDevice::ExitPresent(VRServiceImpl* service) {
-  if (IsPresentingService(service))
-    presenting_service_ = nullptr;
-
-  gvr_provider_->ExitPresent();
-  OnExitPresent(service);
+  if (IsPresentingService(service)) {
+    gvr_provider_->ExitPresent();
+    OnExitPresent();
+  }
 }
 
 void GvrDevice::SubmitFrame(VRServiceImpl* service, mojom::VRPosePtr pose) {