Prevent fractional positioning in systray HiddenItemsView
Before this patch, the icons of the elements in the systray window were always blurry. Especially the 1-px outline of the highlight did not look good at all. This was also the case when the view was not scrolled.
Before:
After:
I'm not entirely sure if this is related to bug 432130.
Commit message:
Fix a visual glitch that caused the icons and highlight of the items in
the HiddenItemsView of the systray to be blurry. This commit fixes this
by preventing the items from being positioned in a non-integer position.