Google has been working on various bottom toolbar interfaces for Chrome since late 2016. First, the address bar was moved to the bottom of the screen ('Chrome Home'), then Google began experimenting with moving various buttons to the lower part of the screen ('Chrome Duet'). Now the Chrome developers are trying something else — adding a tab switcher to the bottom.
This is still in the very early stages of development, as it doesn't even have a flag toggle yet. The below screenshots come from XDA Developers, who activated the feature through unknown means.
While the regular tab switcher can still be accessed from the top right button (at least for now), the new toolbar offers a way to quickly switch between tabs with just one tap. It's definitely a good use of the 18:9 (or taller) screens that many smartphones now have.
- XDA Developers