Show running app window when app in Unity dock is hovered for 2-3 seconds

This will increase user-friendliness of the Unity. When a running app in Ubuntu dock is hovered for 2-3 seconds (or can be set for instant), then app window (full window and not its thumbnail) should be temporarily shown (as thumbnails is shown in Windows for running apps at taskbar). As the mouse is moved from that app, its temporarily shown window should also be removed. This will help users to easily see their running app windows and decide which app they need to run. For example, I am running Downloads and Firefox, I just hover my mouse on Downloads and I can see whether my downloads are complete (if not, then I won't open that).