STR: - ensure the currently selected tool in the tools is the performance tab - restart nightly - open a page, say ars technica - open the toolbox, perf tool shoud be active, ten immediately start recording Expected results - should see normal fps graph, topping out at 60fps. Actual: sometimes erroneous results, like 300fps are shown, sometimes it's completely blank. Suspect the graph isn't completely 100% ready to start showing data? See screenshot: https://www.evernote.com/l/AAEkXIHKVGtM0ouvPZ-RMOYMS9sci2mrmuQB/image.png

Suspect yet another issue of docshell times. Hopefully bug 1152829 fixes this.