Adding a few more people to cc.

What the bug looks like, before applying https://chromium-review.googlesource.com/c/chromium/src/+/739488

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/dd306bed2d51f5414dcb3cb88c882ab1f22fd395

commit dd306bed2d51f5414dcb3cb88c882ab1f22fd395
Author: Jean-François Geyelin <jif@chromium.org>
Date: Fri Oct 27 11:35:26 2017

Force a relayout of the Stackview before setting up the animations.

Also changes the vertical Autoresizing mask of the StackViewToolbar to
accommodate the variable height of the toolbar.

Bug:  777866 
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I1826947dc6fd529e3f71afcc46958db5371b1028
Reviewed-on: https://chromium-review.googlesource.com/739488
Commit-Queue: Jean-François Geyelin <jif@chromium.org>
Reviewed-by: Kurt Horimoto <kkhorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#512149}
[modify] https://crrev.com/dd306bed2d51f5414dcb3cb88c882ab1f22fd395/ios/chrome/browser/ui/stack_view/stack_view_controller.mm
[modify] https://crrev.com/dd306bed2d51f5414dcb3cb88c882ab1f22fd395/ios/chrome/browser/ui/stack_view/stack_view_toolbar_controller.mm

[Auto-generated comment by a script] We noticed that this issue is targeted for M-63; it appears the fix may have landed after branch point, meaning a merge might be required. Please confirm if a merge is required here - if so add Merge-Request-63 label, otherwise remove Merge-TBD label. Thanks.

This bug requires manual review: M63 has already been promoted to the beta branch, so this requires manual review
Please contact the milestone owner if you have questions.
Owners: cmasso@(Android), cmasso@(iOS), gkihumba@(ChromeOS), govind@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

Please verify in Canary

Animation doesn't look good look time. Please find the attached video.
https://drive.google.com/file/d/0B-xmXLQhjeKubjJuQzRYUVBJdVE/view
Also note that the tab width is not adjusted correctly after following the steps from comment#0.

Build: 64.0.3254.0 canary
Device: iPhoneX Simulator.

Is my understanding that this cannot be verified in Canary as it is simulator only at the moment?

Removing the RBS and moving this to M64 as the flag won't be enabled in M63.

Fixed by https://chromium-review.googlesource.com/c/chromium/src/+/757071

Verified in 64.0.3282.75 beta, iPhone X iOS 11.2
The animation when entering the StackView after a rotation looks good.
https://drive.google.com/file/d/1kF4mGP4pVrt3DTehjyhwngZSe7a_S6ky/view