[webrtc-stats] WebIDL issue

vivienlacourba has just created a new issue for https://github.com/w3c/webrtc-stats:

== WebIDL issue ==
Hi @alvestrand 
The WebRTC respec ci issue should be fixed, but respec is now reporting a WebIDL issue in webrtc-stats.
Also if you have any pending PR you should rebase them.

```bash
$ cd webrtc-stats
$ git checkout master
$ git pull
$ make update
$ make check
(...)
😱 ReSpec error: Failed to parse WebIDL: `Got an error during or right after parsing `partial dictionary RTCRTPStreamStats`: Bodyless dictionary`.
        <details>
        <pre>partial dictionary RTCRTPStreamStats : RTCStats {
DOMString           mediaType;
double              averageRTCPInterval;
};
 Got an error during or right after parsing `partial dictionary RTCRTPStreamStats`: Bodyless dictionary, line 1 (tokens: ': RTCStats {')
[
    {
        "type": "other",
        "value": ":"
    },
    {
        "type": "whitespace",
        "value": " "
    },
    {
        "type": "identifier",
        "value": "RTCStats"
    },
    {
        "type": "whitespace",
        "value": " "
    },
    {
        "type": "other",
        "value": "{"
    }
]</pre>
        </details> 
make: *** [build/output.html] Error 1
```

Please view or discuss this issue at https://github.com/w3c/webrtc-stats/issues/337 using your GitHub account