mozilla/lightbeam — pull request #638 by jvilladsen (2014-12-14 17:17:13+00:00)
Title: Keep graph in view when zooming in

If you zoomed out, moved the graph and then zoomed in again, the graph could be moving out of sight.
The reason is that the zoom would be zooming towards/away from the centre of the visible area.
This is changed to instead zoom towards/away from the graph, which is around position (350, 350).