Bug 346131

It is easy to maximize window to left/right half of the screen by dragging it to edge of the screen. So it is easy to place two windows side by side. But sometimes it is handful to place windows above each other (top/bottom half of the screen), for example when comparing documents/config files with long lines or wide tables. And there is no easy way to maximize a window to top/bottom half of the screen.

Dragging a window to bottom edge is easy, it can be handled the same way as left/right edge. Top edge is a bit tricky since it is used for normal maximalization (full screen). So lets use left/right third of the top edge to maximize to upper half of the screen, and middle of the edge to full screen. 

Reproducible: Always