[573009] autoscrolling on editor border had wrong offset

The autoscrolling mechanism which ensured that the canvas automatically
scrolled when the mouse was across the border of the editor used a wrong
mouse offset. This resulted that when the palette was folded
autoscrolling was not working.

Bug: https://bugs.eclipse.org/bugs/show_bug.cgi?id=573009
Change-Id: I9f63b1962700dd4006f39aa25d5f47f0640e1a8c
1 file changed