835544 - Unpurple nsEventListenerManager right before we CC

Status: NEW

(Core :: Cycle Collector, defect)

Description

[Andrew McCreight [:mccr8]]

I see 4 of these in my CC graph (putting a few dozen other things into the CC graph), occasionally, when I look at the CC logs with TechCrunch open.  I think we purge these from the purple buffer during JS cleanup, because they can't be made skippable directly.  I wonder how feasible it would be to do a pass right at the start of the CC, that doesn't do any of the unmark gray stuff, just to clear these out.

Comment 1

[Olli Pettay [:smaug][[e-mail]]]

We purge them from purple buffer during js cleanup because we want to do black-bit-propagation and 
can just at the same time remove purple-ness.

But We could indeed check whether mTarget is certainly alive, in which case ELM is alive.
When you see ELMs in the graph, are they roots?

Comment 2

[Andrew McCreight [:mccr8]]

Attachment: TechCrunch graph, after nsPresContext is removed

Yes, they are roots.  This is what the CC graph is, where purple are things in the purple buffer, and red is XPConnect roots (possibly overlapping with purple things)