Able to reproduce the issue in Android.

Steps to Reproduce:
1. Open a blank incognito tab
2. Tap on tab switcher button
3. Animation of "+" is not proper

Chrome versions tested:
63.0.3239.83, 65.0.3292.0, 58.0.3029.125

OS:
Android 8.0.0

Android Devices:
Pixel XL, 8.0.0 Build/OPR1.170623.027

Please find the screen cast in the below URL --
go/chrome-androidlogs/794352

This is a Non-Regression issue observed from M58 builds.


Thanks!!

WAI, the toolbar is an android view that we clip while the composited tab is moving into its place. We won't be able to fix this without an overhaul of how the toolbar works.

Is there a reason why UI glitch is WAI? I understand that it may be hard to fix the bug, but it does not mean that this is not a bug. There are 2 ways how to treat bugs:
 - as a list of known problems 
 - as a list of TODOs

Are Android bugs are just list of TODOs? If so, then I can understand why WontFix is the right resolution here, but is it really WAI?

Yes, this is really WAI. It isn't just the tab switcher button, it is the entire toolbar (menu and tab switcher as well). This was the solution that we came up with the make the transition look better. If the request is to redesign the transition, we can open a discussion with design about it, but as far as engineering is concerned this isn't a bug.

As a side note, modern design makes this decidedly less noticeable.

This bug is about UI glitch, which is a real thing which you can see on the screenshot. I don't think I should be arguing but I still can't understand why Chrome for Android intentionally choose to have UI glitches (WAI means works as intended).