We decided to temporarily back out the new tab animations until we're able to do more user testing and validation of the new animations. While they may have some potential perf wins on the book, it's less clear if it can be perceived as an improvements, and UX doesn't think the new animation as implemented is as pleasing as the existing one.

Since there are a few bugs to be fixed with them, and we'll put engineering efforts on hold until we have new directions to continue, it's better to remove them from the tree so that people don't get stuck with them (and e.g. bug 1526112) for too long.

https://hg.mozilla.org/mozilla-central/rev/70dfe7fae016

Comment on attachment 9053724 [details]
Bug 1539255 - Back out new tab animations. r=dao

Beta/Release Uplift Approval Request

• Feature/Bug causing the regression: Bug 1355588
• User impact if declined: Feature is not ready to roll out, so we should must back it out from beta
• Is this code covered by automated tests?: No
• Has the fix been verified in Nightly?: No
• Needs manual test from QE?: No
• If yes, steps to reproduce:
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky):
• String changes made/needed: None

Comment on attachment 9053724 [details]
Bug 1539255 - Back out new tab animations. r=dao

Back out an experimental feature due to existing bugs and UX decision, uplift approved for 67 beta 7, thanks.

https://hg.mozilla.org/releases/mozilla-beta/rev/d511bf7fa222