We should keep consistent split rule for wallpaper and other home menu
item. So, we create this cl to register the split rule for wallpaper.
Also, I do some minor refactoring in this cl for reusing existing
method and better code quality.
Test: Go to wallpaper, and click back key. App can close.
Fix: 204406425
Fix: 204364572
Change-Id: Ia7de9483b351d1121cc26c4af1cb8a89ad0a16bc