The fourth-generation MacBook Pro has no escape key.

[rawles]

The fourth generation MacBook Pro has no escape key, but instead a multi-touch OLED strip. However, the upper left key is the backtick (`) unshifted and the tilde (~) shifted. The backtick currently inserts a long dash. Should we put this on a command, and make the backtick do the same thing that the escape key does now?

[hairydalek]

Probably worth finding out more about how the key strip works, and whether the Esc Key is displayed when browsers are running. It may also be that you can "educate" the browser to display the escape key.

https://9to5mac.com/2016/10/28/new-macbook-pro-touch-bar-details-ui-interactions-screen-specs-control-strip-and-how-third-party-apps-can-use-it/

Apple's HIG documentation: https://developer.apple.com/library/content/documentation/UserExperience/Conceptual/OSXHIGuidelines/AbouttheTouchBar.html

[ZXGuesser]

It may show Esc on the system button for browsers anyway. That seems to be the case for most standard programs judging by screenshots.
If not Ars report that Apple say you can set the bar to normal function keys in keyboard settings, or temporarily switch to them by holding the Fn key.