Backout 1a99d532ccd6:ac7fc104c829 (bug 812813) due to bc test failure

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rename : browser/themes/gnomestripe/downloads/download-notification-start.png => browser/themes/gnomestripe/downloads/download-notification.png
rename : browser/themes/pinstripe/downloads/download-notification-start.png => browser/themes/pinstripe/downloads/download-notification.png
rename : browser/themes/winstripe/downloads/download-notification-start.png => browser/themes/winstripe/downloads/download-notification.png