See attached video. Somehow I can only reproduce this when opening new windows, I don't see it with the first window during startup. There are 7 frames where the activity stream about:home page is displayed with an empty Pocket section, causing a vertical scrollbar. Then it disappears, the scrollbar too, and everything else shifts to the right due to the space freed by the scrollbar.

(In reply to Florian Quèze [:florian] [:flo] from comment #0) > Somehow I can only reproduce this when opening new > windows, I don't see it with the first window during startup. Actually I just saw it during startup now.

Fixed by https://github.com/mozilla/activity-stream/pull/3622 to be uplifted in this bug.

Comment on attachment 8913266 [details] Bug 1400920 - The pocket section briefly shows up and causes the scrollbar to make the whole page flicker. https://reviewboard.mozilla.org/r/184648/#review189830 Thanks!

Pushed by edilee@gmail.com: https://hg.mozilla.org/integration/autoland/rev/dd4eea6b8ae4 The pocket section briefly shows up and causes the scrollbar to make the whole page flicker. r=ursula

Verified fixed on Nightly 58.0a1 20170929100122

Comment on attachment 8913266 [details] Bug 1400920 - The pocket section briefly shows up and causes the scrollbar to make the whole page flicker. Approval Request Comment [Feature/Bug causing the regression]: Activity Stream prerendering [User impact if declined]: Users who don't see Pocket (only shown for US/CA/DE) might see content jumping around horizontally as scrollbars appear then disappear. [Is this code covered by automated tests?]: No, this is just a css change [Has the fix been verified in Nightly?]: Yes, 20170929100122 [Needs manual test from QE? If yes, steps to reproduce]: No [List of other uplifts needed for the feature/fix]: None [Is the change risky?]: Not really [Why is the change risky/not risky?]: Only changing 1 line of css (and strings) [String changes made/needed]: Pontoon localized strings were added that are not exposed for localization via mozilla-central

Why do we have unrelated string changes in this patch?

flod suggested that we keep the strings up to date through the beta 57 cycle, but I can just manually edit the patch to not have strings, but the manual steps could introduce risk in the activity stream export process. Should I reattach a manually edited export patch without strings and request uplift a strings-only patch later in the beta process?

Yeah, clearly, I would like a bug == one issue being fixed, no unrelated changes.

Comment on attachment 8913266 [details] Bug 1400920 - The pocket section briefly shows up and causes the scrollbar to make the whole page flicker. This is needed to fix Bug 1404345, Beta57+

(In reply to Ed Lee :Mardak from comment #9) > [Is this code covered by automated tests?]: No, this is just a css change > [Has the fix been verified in Nightly?]: Yes, 20170929100122 > [Needs manual test from QE? If yes, steps to reproduce]: No Setting qe-verify- based on Ed's assessment on manual testing needs and the fact that this fix has automated coverage.