the Web IDL dependency

So we're in the odd situation with JSON-LD-API of needing a normative 
reference to WebIDL, which might stay stuck in CR for some time.  In 
this case, however, we can proceed to REC, even with it in CR, by 
following these instructions:

    You'll need to provide evidence that the WebIDL used in your spec is
    stable, as follows:
    [[
    To provide evidence that your WebIDL is stable and tested, you could use
    idlharness.js. Example at [1] and run it against Firefox nightly and
    IE10. idlharness.js doesn't cover all of WebIDL. If you run into a
    limitation, contact Robin Berjon and he might be able to help.

    [1]
    http://w3c-test.org/webperf/tests/approved/UserTiming/idlharness.html
    ]]

I don't actually understand this at all.   I'm hoping some other people 
do.   If not, I'll work harder to figure it out.

       -- Sandro