App Version (from "Chrome Settings > About Chrome"): 73.0.3674.0 canary
iOS Version: 12.1.2
Device: iPhone XS

Steps to reproduce: 
0. Kill off any running Chrome Canary.
1. Create a new tab
2. Turn phone to landscape
3. Scroll up to the first "Articles for you" and tap on it.

Observed behavior: 
The page is loaded in landscape (with the right side of content area displayed in gray).

Expected behavior: 
Web page should be rendered to the full width of landscape.

See video: https://drive.google.com/open?id=1Yp4n6VLePo97ckw3lbo3l0GDmaMSodnt

Note: This works fine with 72.0.3626.51 beta (TestFlight).