Sure, I'd be more than happy to try breaking this down, I'm going to try a nightly build now as other users have suggested and see how it feels
Excellent, thanks!
If you're using a nightly, you should be able to use https://developer.mozilla.org/en-US/docs/Mozilla/Performance... to profile it, because nightlies have useful symbols. Might be worth capturing a profile at the point when the spinner stops and the page is finally shown.
The issue appears to have resolved itself with a fresh install. I could not replicate the behavior in the nightly, and when I reinstalled the main release it did not manifest again either. Sorry to not be a better help, I'm trying to wrap my head around it...
All good. It's frustrating when problems come and go like this, but not much we can do about it.
If this starts happening again and you get any more data on it, please email me: bzbarsky at mit dot edu.
Is there a particular site that causes this to happen when you have it loaded? If you're willing to spend some time troubleshooting or profiling this, please let me know and I'll walk you through some ways to do that...