title: Multiple form ID's in HTML5's input form attribute
body: <p>The HTML5 input element includes a 'form' attribute, which can contain one or more space delimited form id's. See below for a simplified example, where both form1 and form2 share an input element.</p>
  
  <pre><code>&lt;form id="form1" method="post"&gt;
      &lt;input type="submit"&gt;
  &lt;/form&gt;
  
  &lt;form id="form2" method="post"&gt;
      &lt;input type="submit"&gt;
  &lt;/form&gt;
  
  &lt;input type="text" form="form1 form2"&gt;
  </code></pre>
  
  <p>At least, that's how it's supposed to work:<br>
  <a href="http://swatelier.info/at/forms/HTML5attrib.asp">http://swatelier.info/at/forms/HTML5attrib.asp</a><br>
  <a href="http://www.w3schools.com/tags/att_input_form.asp">http://www.w3schools.com/tags/att_input_form.asp</a></p>
  
  <p>In Chrome 28, I see that adding a second form id hides an input element from both forms. What modern browsers, if any, support this functionality?</p>