I noticed a bug where the following can happen. The parent sends a TrackCookiesLoad message followed by an HTTP OnStartRequest message. When these messages are received in the child, the TrackCookiesLoad message goes in the SystemGroup event queue and the OnStartRequest message goes in the event queue for the relevant tab. Unfortunately, this means that the OnStartRequest message could run first since the queues have no guaranteed ordering. We really should be putting the TrackCookiesLoad message in the same queue that the OnStartRequest message goes in. I worked on that a little bit, but it's hard to get right. For now, I would like to leave the cookie message unlabeled. Any unlabeled message/event is totally ordered with respect to all other messages/events, so this fixes the bug. We'll definitely have to fix the labeling in the future since this message is very common. But I'd like to fix the bug ASAP.

Comment on attachment 8906221 [details] [diff] [review] patch Review of attachment 8906221 [details] [diff] [review]: ----------------------------------------------------------------- Mmm, this is a delightful issue to watch out for in the future.

Pushed by wmccloskey@mozilla.com: https://hg.mozilla.org/integration/mozilla-inbound/rev/a4eac2ea9733 Don't use SystemGroup for CookieServiceChild (r=jdm)