QWebEngine: Unrecognized Content-Security-Policy directive 'require-trusted-types-for'

When trying to login to Google (other websites may also be affected) the WebEngine logs a Unrecognized Content-Security-Policy directive 'require-trusted-types-for' error message and the web site rejects the login.

This can be reproduced with the simplebrowser example delivered with QWebEngine.

I did the following:

• Build the simplebrowser example without any modifications
• Run simplebrowser
• Go to https://www.google.com
• Open Web Inspector in new window
• Click "Sign in"
• Enter user name (e-mail)

I expect

• That the web site asks for my password

What happens

• The web site denies the request, complaining about the security of the browser:
  "This browser or app is probably insecure"
• The web console of the Web Inspector displays the error message
  "Unrecognized Content-Security-Policy directive 'require-trusted-types-for'.  bscframe:1"

The problem occurs on the platforms listed above, but may not be limited to those.