[dom] Spec for DOMTokenList stringifier disagrees with every single implementation (#105)

It looks like the spec for this got changed in 2012 in <https://github.com/whatwg/dom/commit/8deff0eb9275dadec6fd41cc9eaeec93ee14bb54>, after all browsers had already interoperably implemented the previous spec.  Simple testcase:

    <div class=" a   b   c "></div>
    <pre id="log"></pre>
    <script>
      document.querySelector("pre").textContent = 
        document.querySelector("div").classList;
    </script>

Per current spec, the value in the `<pre>` should be:

    a b c

but all of Firefox, Chrome, Safari, IE (edge) make it 

     a   b   c

(with leading and trailing whitespace).  You can see a live testcase at http://jsfiddle.net/e3LwzL9d/

It's probably a good idea to revert to the old behavior, and similarly to have the `DOMSettableTokenList` getter for `value` just get the attribute value, so it stays in sync with the stringification behavior.  You can see a testcase for that case at http://jsfiddle.net/e3LwzL9d/1/ and it looks like this:

    <iframe sandbox=" a   b   c "></iframe>
    <pre id="log"></pre>
    <script>
      document.querySelector("pre").textContent = 
        document.querySelector("iframe").sandbox.value;
    </script>

Again, all browsers that implement `DOMSettableTokenList.value` (IE, Chrome, Firefox) return

     a   b   c 

here, not

    a b c

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Reply to this email directly or view it on GitHub:
https://github.com/whatwg/dom/issues/105