The observers added here: http://mxr.mozilla.org/mozilla-central/source/dom/browser-element/BrowserElementChildPreload.js#256 http://mxr.mozilla.org/mozilla-central/source/dom/browser-element/BrowserElementPanning.js#61 never get removed and build up over the course of mochitest runs. Please note that the correct solution here is not to make the BrowserElementPanning observers weak observers; we should instead make the BrowserElementChildPreload observers strong observers and then properly manage the lifetime of all the observers.

Turns out we can just remove the observers at unload. I'm less sure of how to address BrowserElementPanning's observers, as BrowserElementChildPreload can't (I don't think) see the ContentPanning variable defined therein. Registering an unload handler for ContentPanning would work, I suppose. Do you have any preferred course of action here?

Comment on attachment 8362677 [details] [diff] [review] don't register weak observers in BrowserElementChildPreload.js Review of attachment 8362677 [details] [diff] [review]: ----------------------------------------------------------------- I'm fine with trying to use an unload handler for BEPanning too. ::: dom/browser-element/BrowserElementChildPreload.js @@ +100,5 @@ > > return null; > } > > +const OBSERVED_EVENTS = [ I would prefer kObservedEvents, but no big deal if you want to stick with UPPER_CASE

(In reply to Fabrice Desré [:fabrice] from comment #2) > I'm fine with trying to use an unload handler for BEPanning too. OK, great, I'll just add that in a separate patch. > ::: dom/browser-element/BrowserElementChildPreload.js > > +const OBSERVED_EVENTS = [ > > I would prefer kObservedEvents, but no big deal if you want to stick with > UPPER_CASE I went with UPPER_CASE because that seemed to be the prevailing style in that file.

...and here's the equivalent patch for BrowserElementPanning.js.

Blocks a blocker. Let's uplift this to 1.3.

https://hg.mozilla.org/releases/mozilla-aurora/rev/662ce8f620a9 https://hg.mozilla.org/releases/mozilla-aurora/rev/299ddf0c23a8