We mark some events as temporary when dispatching, for the sole reason of manually calling forgetDOMObject when done dispatching. There doesn't seem to be any reason to call it manually, as JSEvent destructor will do this automatically right away. Patch forthcoming. Please let me know why I'm wrong :-)
Created attachment 24521 [details] proposed patch
Comment on attachment 24521 [details] proposed patch r=me
Committed revision 37718 and 37719.