Route VR lifecycle through platform services

src/app_events.cpp

@@ -264,6 +264,16 @@ void App::request_app_close()
     active_platform_services().request_app_close();
 }
 
+bool App::start_platform_vr_mode()
+{
+    return active_platform_services().start_vr_mode();
+}
+
+void App::stop_platform_vr_mode()
+{
+    active_platform_services().stop_vr_mode();
+}
+
 void App::attach_ui_thread()
 {
     active_platform_services().attach_ui_thread();