App Version: 69.0.3947.22 beta
iOS Version: 10.3.3, 11.4.1, 12 beta 5
Device: iPhone, iPad

Steps to reproduce:
1. Launch chrome 
2. Open multiple new tab pages
3. Change the device orientation to landscape
4. Tap on tab switcher icon
5. Add few more tab pages in landscape orientation
6. Change the device orientation to portrait
7. Tap on tab switcher icon

Observed results:
Notice that animation is not smoothing while displaying tabs of tab grid

Expected results:
Animation of tab grid should be smooth

Number of times you were able to reproduce: 5/5
Bug reproducible after clean install: Yes/No
Bug reproducible after clearing cache and cookies: Yes/No
Bug reproducible on Chrome Mobile on Android: Not tested
Bug reproducible on Safari/Firefox: Firefox: NA, Safari: NA
Bug reproducible on current stable build (App Version, iOS Version): No on M68 (UI Refresh not available)
Bug reproducible on the current beta channel build (App Version, iOS Version): Yes on M69 

Link to video:
https://drive.google.com/file/d/1ds_vs8jVPTLuUohBhGSK-nV23NIk1Wzv/view?usp=sharing