I was updating the throbber for the social sidebar for bug 750054, and noticed a couple of issues: * The throbber is applied to a toolbarbutton that normally uses a spritesheet. That's done using -moz-image-region, which isn't reset when attempting to show the throbber - so the throbber is never visible * The toolbarbutton's image element (.toolbarbutton-icon) is explicitly set to 18x18 pixels. So even if the (16x16) throbber did display, it would be stretched I've opted to contain the scope of 750054, so I've only updated the URL the CSS references for the throbber image. I haven't updated it to use the HiDPI version of the throbber, since that's only going to make the code more broken without the above fixes.
deprecation in fx51