Re: [dom] Added an example showing feature detection with supports() (#144)

> @@ -8705,6 +8705,25 @@ associated <a for="/">element</a>'s
>    <p>Throws a <code>TypeError</code> exception if the associated attribute has no supported tokens defined.
>  </dl>
>  
> +<p>The <a method for=DOMTokenList lt="supports()">supports()</a> method can be used to detect support for {{DOMTokenList}} tokens:
> +
> +<pre class=lang-javascript>
> +var DOMTokenListSupports = function(tokenList, token) {
> +    if (!tokenList || !tokenList.supports) {
> +        return;
> +    }
> +    try {
> +        return tokenList.supports(token);
> +    } catch (e) {
> +        console.log("The DOMTokenList doesn't have a supported tokens list");

I'm not sure why we are catching this exception, and showing an example of people using `domTokenListSupports` on classList. We should not show examples of people doing wrong things, and definitely should not encourage them to write error-handling code for such programmer errors.

I'd remove the try/catch, and maybe if you still want to let them know that classList will throw, you should just add a comment at the end of that line like "will throw since classList has no supported tokens list"

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