Last modified: 2014-05-19 23:22:36 UTC
Add an item to the tab area with class "collapsible" and display none applied. Then make the window narrow (so it moves into the vector menu), and expand again (so it becomes a tab again). The item is now visible when it was previously hidden. vector.collapsibleTabs.js should not override this state.
I am tempted to WONTFIX this. This bug is actually a proposed way of solving bug 65292 in VisualEditor and not a real bug in core. If a tab is supposed to be treated as not being there, then it just should be removed from the DOM (and bug 65292 has a pending patch that does this).
Bug 65292 was fixed in a different way, so let's close this.
I'm not sure that this is the right call, but I also don't really care. :-)