[mediaqueries-5] ToC queries

[fantasai]

https://lists.w3.org/Archives/Public/www-style/2015Dec/0188.html

Request was for querying whether the device presents a usable ToC (and therefore the page's own should be suppressed).

[tabatkins]

Some additional points raised by Florian, copied here for convenience:

• Does the reader always generate a TOC (epub), or only if the gcpm bookmark properties are used to mark the outline?
• Is the TOC-in-the-UI major part of the UI that users will for sure see (epub readers), or some side feature they might not know about (like the "info" panel in opera desktop 12)

And a digipub thread on the subject for some additional discussion.