AccessibilityChecker identifies errors in its own built-in IFrame

[raphael-kalff]

We've recently discovered 3 unknown errors that previously didn't exist.
AccessibilityChecker references 3 errors inside it's built-in iframe:

• Iframe element requires a non-empty title attribute that identifies the frame.
• A title should be provided for the document, using a non-empty title element in the head section.
• The html element should have a lang or xml:lang attribute which describes the language of the document.

If we check the option "skip Iframes", the amount of errors reduces down to 2. It will ignore the first issue with the title attribute but the remaining ones are still visible.