What happens if the sidebar is hidden, then the window is shrunk down a bunch, then the sidebar is shown?  It seems like there'd be nothing clean we could do to prevent the editor from falling below the min at that point.  The only options I can think of are (a) programmatically resize the whole window larger, which is pretty weird; (b) refuse to show the sidebar, which would look like a bug; or (c) when calculating window min size and status bar is invisible, factor in the saved sidebar width that it would get restored to if shown, which is a bit weird too.

I wonder if it's simpler, rather than using this approach, so just set a min-width on the container of the UI in question (panel header?) and have it clip with `overflow: hidden` after that.  That seems like a more "webby" approach to the problem -- and will be a better answer for in-browser versions of Brackets anyway, since we can't actually enforce a min window size there anyway.

@bchintx, thoughts?  (CC @njx too, since I think the 'editor area min width' thing was originally your suggestion, in #5507)