title: Firfeox 87 on Ubuntu throws TypeError for RTCRtp[Sender|Receiver].getCapabilities
body: <p>Is it a bug that Firefox throws a <code>TypeError</code> when <code>RTCRtp[Sender|Receiver].getCapabilities(&quot;video&quot;)</code> is executed in the Developer Tools console?</p>
  <p>Firefox version is 87.0 with build number 20210318103112 on Ubuntu 20.04.<br />
  For comparison, Chrome Version 90.0.4430.40 (Official Build) beta (64-bit) returns the expected object containing <code>codecs</code> and <code>headerExtensions</code>.</p>
  <p>The full error message for <code>RTCRtpSender.getCapabilities</code> in Firefox Developer Tools console is:</p>
  <pre><code>Uncaught TypeError: RTCRtpSender.getCapabilities is not a function
      &lt;anonymous&gt; debugger eval code:1
  </code></pre>
  <p>A screenshot of the Firefox Developer Tools showing the error and the Firefox version number:
  <a href="https://i.stack.imgur.com/acTKU.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/acTKU.png" alt="Screenshot showing error in Firefox 87 Developer Tools console" /></a></p>