Version: 54.0.2824.5
OS: ChromeOS

What steps will reproduce the problem?
(1) Install a few apps from the Play Store.
(2) Run one of the apps.
(3) Flip the device into tablet configuration.
(4) Look for a way to full-screen (not maximize) the app.

What is the expected output?

Some fabulous UX to let me full-screen the app. Really really want to be able to run some apps full-screen!

What do you see instead?

There is no way to do that; only the full-screen keyboard key seems to do that.

Bottom of the display is eaten up by the tray area, and the top by the window titlebar, as a result.