With bug 727668 we will be showing the bookmarks toolbar on the New Tab page. Right now this is happening after we determine what page has been loaded so there is a slight pause before the toolbar appears.

I actually can't reproduce this with an opt build - is this based on an automated test or debug builds or something?

I filed this bug in anticipation of some flickering, but then moved the setting of the visibility to earlier in the window load such that this bug wasn't necessary anymore. However, we have since seen bug 1673363 get filed. I'm going to close this bug but not as a dupe since it wasn't actually filed for the same reason as bug 1673363.

If the bug is invalid, then the exception at https://hg.mozilla.org/mozilla-central/rev/45bbeabb0c89cf73d644b59898cb207e4462f147#l18.32 should be removed.

When testing locally on slow hardware, I've noticed that the toolbar initially appears with a smaller height (that's covered by bug 1674091, and could hopefully be fixed). Then the next thing that 'flickers' is when the actual content gets displayed: text and favicons. I think it's fine for these to appear slightly later, but the changed rect detected by the flicker test should be significantly smaller than the size of the whole toolbar.

https://hg.mozilla.org/mozilla-central/rev/af10a3ffbbd1

== Change summary for alert #27839 (as of Tue, 24 Nov 2020 05:05:31 GMT) ==

Improvements:

Ratio Suite Test Platform Options Absolute values (old vs new) 6% sessionrestore sessionrestore linux64-shippable e10s stylo 527.04 -> 497.83 5% sessionrestore sessionrestore linux64-shippable-qr e10s stylo webrender-sw 545.96 -> 516.25 3% sessionrestore sessionrestore linux64-shippable e10s stylo 506.92 -> 492.08 2% sessionrestore sessionrestore linux64-shippable e10s stylo 502.29 -> 492.08

For up to date results, see: https://treeherder.mozilla.org/perfherder/alerts?id=27839

Is this something we should consider for Beta uplift?

(In reply to Ryan VanderMeulen [:RyanVM] from comment #8)

Is this something we should consider for Beta uplift?

I considered this but I found it a bit risky. There's still 1 regression to sort out, at least.

In practice, the performance regressions from bug 1675461 are going to be gone on beta as soon as we leave EARLY_BETA, and are likely no different to what people have experienced / are experiencing on earlier versions if they had the bookmarks toolbar always-enabled. So I think this is better off riding the trains.