Make it easier to drag from device edges

[sorccu]

As reported in https://groups.google.com/forum/#!topic/openstf/KE7I9b8EkgU, dragging from the screen edge to trigger, for example, a side menu, won't sometimes work because you end up resizing the browser instead. Adding some margin would solve the issue, but reduce the available space for the screen itself.

One possible option would perhaps be to wait for a few seconds when the pointer is in close proximity of the screen edges, and then "zoom out" a little bit so that it becomes possible to drag from the edge.