If you hover over the back button, you'll see the multiline tooltip added by bug 619930 (looks like it was a normal single-line tooltip before). If you click-and hold the back button, the history dropdown appears after a short delay (as expected). But a fraction of a second before the dropdown is shown, the tooltip is displayed, and then the dropdown is drawn over it. [If you look very closely, you can see the tooltip behind the OS X semitransparent menu.] Even worse, if you move the mouse by a pixel, the tooltip is redisplayed, this time _over_ the dropdown. It's tall enough to obscure the beginning of the first 3 history entries. I know I've used click-and-hold, but only recently noticed this... Not sure if 619930 made it worse by being multi-line, or if something else changed in more recent builds? Perhaps the more general fix here would be to make tooltips never display when the mouse button is down? Or add an attribute so binding code (eg for menu dropdowns) can temporarily suppress the relevant tooltip?

(In reply to Justin Dolske [:Dolske] from comment #0) > Perhaps the more general fix here would be to make tooltips never display > when the mouse button is down? There's a patch for that in bug 312852 comment 135 which could be resurrected.