Chrome Version: 65.0.3325.65 (tested, 64.0.3282.144 also reported)
OS: Chrome

What steps will reproduce the problem?
(1) Configure the Search key to toggle the search panel.
(2) Install https://chrome.google.com/webstore/detail/window-state-sample/hcbhfbnaaancmblfhdknlnojpafjohbi/related
(3) Launch the app and go fullscreen.
(4) Note that the Tab key navigates through the app.
(5) Press Search twice to toggle the search panel on and off.
(6) Hit Tab.

What is the expected result?
Tab navigation should still work.

What happens instead?
Tab navigation doesn't work until the app is clicked.

Note that this only seems to affect full-screen Chrome apps. Browser windows and windowed apps are not affected.