avoid jumping viewport when process list is changing

[Karl-Philipp Richter]

When the process list changes (new items added or removed due to processes termining and being started), the viewport isn't adjusted and the list simply scrolls up and down making it impossible to get any information from tip popup (important for example for command line which rarely fits into the column width). Currently it is necessary to disable automatic updates in the settings dialog and reload manually if necessary.

Updates should (1 of the following)
  * be triggerable directly from the process tree panel (e.g. next to the update button), on/off is sufficient, a slider (from 0 to x) for update interval would be nicer
  * not influence the change of the viewport of the process list or tree (depending on whether dependecies are activated or not), i.e. the viewport should jump so that the entry stays at the same position in the list. This would allow handling information provided by gnome-system-monitor independent from updates (sorting criteria and interval), but would require a list or tree GUI element that could handle the case that the item moves to the first or last position of the tree from a position in the middle in order to avoid the undesired jumping behavior described above for items switching from 1st/last to a middle position at differnt update steps

[Sebastien Bacher (seb128)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. The issue you are reporting is an upstream one and it would be nice if somebody having it could send the bug to the developers of the software by following the instructions at https://wiki.ubuntu.com/Bugs/Upstream/GNOME. If you have done so, please tell us the number of the upstream bug (or the link), so we can add a bugwatch that will inform us about its status. Thanks in advance.