Background selection style behaves funny with <li> items that have children.

Try dragging from here across all the lines below. Why aren't lines 3 and 5 selected and drawn with the expected red background?

• Line 1
• Line 2
• Line 3
  • Line 3a
  • Line 3b
• Line 4
• Line 5
  • Line 5a
  • Line 5b