Implement an API for vrwm to query if the current vr app is active

The API returns if the client_order 0 layer is visible or not. This
aids in 2D app detection

Bug: None
Test: Manual with permissionsgen & calculator

Change-Id: Id988e61a9f93885e93c28ed83ffaffd84f3bdf15
diff --git a/libs/vr/libvrflinger/display_service.h b/libs/vr/libvrflinger/display_service.h
index 2a71b4a..8e96172 100644
--- a/libs/vr/libvrflinger/display_service.h
+++ b/libs/vr/libvrflinger/display_service.h
@@ -87,6 +87,9 @@
                          const ViewerParams& view_params);
   pdx::LocalChannelHandle OnGetPoseBuffer(pdx::Message& message);
 
+  // Temporary query for current VR status. Will be removed later.
+  int IsVrAppRunning(pdx::Message& message);
+
   // Called by DisplaySurface to signal that a surface property has changed and
   // the display manager should be notified.
   void NotifyDisplayConfigurationUpdate();