Chrome Version: 59.0.3054.0 dev
OS: ChromeOS Minnie

Not sure what triggered this, but all I'd done was resume device from sleep.
Device had three windows, one containing ~10 Docs tabs, one containing GMail and Calendar, another containing a few crbug and codereview tabs.

Task Manager showed the browser process consuming 130% CPU and some "sub-frames" consuming ~30% CPU each.  The sub-frames turned out to be an i-frame in the Hangouts extension background page.

After killing the Hangouts processes, the browser continued to consume 130% CPU, and then at some point Task Manager stopped reporting statistics for any processes (issue 710959)