Actual:
VisibleBoundsInVisualViewport() can return a non-empty rect for invisible elements.

Expected:
When an element can't be seen through the visual viewport, VisibleBoundsInVisualViewport() should return an empty rect.

This happens when an element is clipped by an ancestor element's (think <div>) scrollport.

I found this during https://chromium-review.googlesource.com/c/chromium/src/+/1243246. 
The CL adds gtests (see spatial_navigation_test.cc) that demonstrates this.