Make <select> special in innerText

<select> is a replaced element, but for Web compat we need
to include the text of <option> elements in innerText.
The new text is intended to match the behavior of Gecko,
which in turn is very close to the legacy IE/Edge behavior.

Fixes rocallahan/innerText-spec#5.

source

@@ -11868,7 +11868,21 @@ interface <dfn>DOMStringMap</dfn> {
 
      <li>
       <p>If <var>node</var> has no associated CSS box, then let the result of these substeps be
-      <var>items</var> and abort these substeps.</p>
+      <var>items</var> and abort these substeps. For the purpose of this step, the following
+      elements must act as described if the <span>computed value</span> of the
+      <span>'display'</span> property is not 'none':</p>
+
+      <ul class="brief">
+       <li><code>select</code> elements have an associated non-replaced inline CSS box whose child
+       boxes include only those of <code>optgroup</code> and <code>option</code> element child
+       nodes;</li>
+
+       <li><code>optgroup</code> elements have an associated non-replaced block-level CSS box whose
+       child boxes include only those of <code>option</code> element child nodes; and</li>
+
+       <li><code>option</code> element have an associated non-replaced block-level CSS box whose
+       child boxes are as normal for non-replaced block-level CSS boxes.</li>
+      </ul>
 
       <p class="note"><var>items</var> can be non-empty due to 'display:contents'.</p>
      </li>
@@ -11924,7 +11938,7 @@ interface <dfn>DOMStringMap</dfn> {
   </ol>
 
   <p class="note">Note that descendant nodes of most replaced elements (e.g., <code>textarea</code>,
-  <code>select</code>, and <code>video</code> &mdash; but not <code>button</code>) are not rendered
+  <code>input</code>, and <code>video</code> &mdash; but not <code>button</code>) are not rendered
   by CSS, strictly speaking, and therefore have no CSS boxes for the purposes of this algorithm.</p>
 
   <p class="big-issue">This algorithm is amenable to being generalized to work on <span
@@ -119427,6 +119441,7 @@ INSERT INTERFACES HERE
   Jerry Smith,
   Jesse Ren&eacute;e Beach,
   Jessica Jong,
+  jfkthame, <!-- GitHub -->
   Jian Li,
   Jim Jewett,
   Jim Ley,