WebGL: ReferenceError: GetUnityFocus is not defined

When I try to run our app built for webGL, I get this error after a few minutes:

“An error occured running the Unity content on this page. See your browser’s JavaScript console for more info. The error was: ReferenceError: GetUnityFocus is not defined”

Does anyone have any insight on this?

Can you file a bug with repro steps?