Chrome Version       : 73.0.3635.0
OS Version: OS X 10.14.1, on a Mac laptop

What steps will reproduce the problem?
1. Enable chrome://flags/#create-app-windows-in-app.
2. Install a PWA and run it
3. Navigate somewhere
4. Try two finger swipe to navigate back

What is the expected result?

We navigate back (this works without chrome://flags/#create-app-windows-in-app enabled)

What happens instead of that?

Nothing. :(