Steps to reproduce: 1. Open a new tab (but the home page also works) 2. Load about:preferences 3. Click the back button Expected result: no flicker. Actual result: - at some point, the "Nightly" block in the identity area disappears, and the page action icons appear at the end of the urlbar. The 'about:preferences' url remains displayed. - a few frames later the URL bar is cleared (both the url and the page action icons disappear). As a random guess, I would say this could be related to switching between a no-remote browser for preferences to a remote one for about:newtab. See attached screen recording.

(In reply to Florian Quèze [:florian] (unavailable for Firefox until June 4th) from comment #0) > As a random guess, I would say this could be related to switching between a > no-remote browser for preferences to a remote one for about:newtab. I think this is correct, and as a result this won't hit users very often, so I'd make this p5... except that I'm confused because the URL is updated to about:preferences, and the identity block goes away - but the page action menu doesn't. I don't really understand why that inconsistency happens, unless that's a perf fix for the more usual case where we navigate between 2 remote pages, or something. Anyway, fxperf:p3 it is to balance the p5-ness and the priority of figuring out what's going on here...