See bug 1368208 comment 56: > I think I'll land this with 508816-1.xul disabled. The scroll buttons seem > to suffer from some weird invalidation bug that I can reproduce even in > nightly (e.g. in the all tabs list or in the bookmarks menu). My patch > doesn't seem to make this worse but changes the timing such the reftest now > exposes this bug. I added some logging to _updateScrollButtonsDisabledState to see if it enables/disables the buttons as expected. It does do so, i.e. the buttons' disabled attributes get updated, but it seems that somehow this doesn't necessarily get rendered.
status-firefox58: --- → wontfix
status-firefox59: --- → fix-optional
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