The close button can stay on a previous element in the Timeline sidebar when switching content views while the Timeline sidebar is not the current sidebar. See this video around the 4 second and 9 second marks. http://timothy.hatcher.name/demo-timelines-139526.mov
<rdar://problem/19281589>
*** Bug 142168 has been marked as a duplicate of this bug. ***
This issue will go away with tab based UI. Either because we won't show inline resource views next to the timeline sidebar, or because we won't have content browser that confuses this code.