xrEndFrame with 0 layers in an overlay app is not throttled
Unsure if this is expected behavior, but frame loop that ends with an xrEndFrame
with 0 layers is not throttled. Meaning the application can loop as quickly as it wants. And with each loop, the predicted display time moves forward by one frame. When the application finally submits something, its display time could be in distant future, giving an appearance of application hanging.