Inconsistent Rendering/Input Delay between Multiple Windows

In this lightly modified version of the bevy `multiple_windows` example used for testing multi-window picking:

https://github.com/aevyrie/bevy_mod_picking/blob/master/examples/multiple_windows.rs

There is a consistent delay in response between windows. The primary window always updates after the secondary window, regardless of which window is being interacted with when picking. It appears to be a couple frame delay.

For reference, this is what it looks like: