Noticed several instances of this JS Error go by in my terminal, when running a debug build: { JavaScript error: resource:///modules/NetworkPrioritizer.jsm, line 88: TypeError: aBrowser.adjustPriority is not a function } billm, looks like you added these in bug 666804: http://hg.mozilla.org/mozilla-central/diff/9b90ce080a83/browser/modules/NetworkPrioritizer.jsm Has this function gone away or something?

(This was in a debug build, with e10s enabled [default], based off of mozilla-central changeset 754579ec0e68)

No, it's still there. Usually this sort of thing happens when we call the function on a <browser> element whose XBL has already been torn down. Does this happen around the time you close a tab?

Nope, it's happening when I'm switching tabs. (Fresh profile, too. I've just been loading treeherder and a few data URLs, basically. I killed the child process once, earlier, & let it respawn; maybe that's involved?)

Couldn't reproduce in a separate fresh profile, though. In my profile that reproduces this (still running), Bill and I poked around a bit in the Browser Toolbox debugger; didn't find much beyond confirming that the XBL-hooked-up properties don't seem to be there on my tabs' aBrowser objects in this session.

NetworkPrioritizer.jsm has been removed.