draggable goes out of containment, a few pixels in each drag

Please look at this fiddle: http://jsfiddle.net/e2yfC/255/

Drag the thing to the bottom edge, it will stop there at first. But then stop dragging and start dragging down again, and it will go a few pixels down. And you can repeat it to make it go farther, and it also works for the right edge, but not the top and left. Whenever you start dragging down/right and the thing already touches the borders, you can go a few pixels farther away from the containment.

Resizable does not seem to be affected by a similar bug, so it does calculate the bounds correctly.

Tested in Firefox 25.0.1 and Chrome 31.