Make <option>'s form getter use the nearest ancestor select

Now that option elements can be any descendant of a select element, this algorithm needs to look higher than just its parent for a select element.

Fixes #11708.

Author: josepharhar

source

@@ -57287,14 +57287,17 @@ interface <dfn interface>HTMLOptionElement</dfn> : <span>HTMLElement</span> {
   </div>
 
   <div algorithm>
-  <p>The <dfn attribute for="HTMLOptionElement"><code data-x="dom-option-form">form</code></dfn> IDL
-  attribute's behavior depends on whether the <code>option</code> element is in a
-  <code>select</code> element or not. If the <code>option</code> has a <code>select</code> element
-  as its parent, or has an <code>optgroup</code> element as its parent and that
-  <code>optgroup</code> element has a <code>select</code> element as its parent, then the <code
-  data-x="dom-option-form">form</code> IDL attribute must return the same value as the <code
-  data-x="dom-fae-form">form</code> IDL attribute on that <code>select</code> element. Otherwise, it
-  must return null.</p>
+  <p>The <dfn attribute for="HTMLOptionElement"><code data-x="dom-option-form">form</code></dfn>
+  getter steps are:</p>
+
+  <ol>
+   <li><p>Let <var>select</var> be <span>this</span>'s <span><code>option</code> element nearest
+   ancestor <code>select</code></span>.</p></li>
+
+   <li><p>If <var>select</var> is null, then return null.</p></li>
+
+   <li><p>Return <var>select</var>'s <span>form owner</span>.</p></li>
+  </ol>
   </div>
 
   <div algorithm>