This does two distinct things:
1. while in immersive mode forces events to land on the window for reveal.
2. when window is not maximized/fullscreen/pinned forces events occurring within kResizeInsideBoundsSize to to go the window.

(2) is straightforward, it's not clear if (1) should be in mus, mostly because it isn't clear how immersive mode should work at this point for mash.