Squash Compositing Hover

Test overlap is rendered correctly when hovering over elements

Case 1, original layer tree:

Case 2: hovering over the "middle" element (causes that div to become its own composited layer)

Case 3: hovering over the "middle2" element (causes that div to become its own composited layer)

Case 4: hovering over the "top" element (causes that div to become its own composited layer)

Case 5: back to situation in case 1