Allow heading content within legend and summary elements

Closes #4990.

Author: scottaohara

source

@@ -16213,7 +16213,7 @@ isn't his only passion. He also enjoys other pleasures.</p>
    <dd><span>Palpable content</span>.</dd>
    <dt><span data-x="concept-element-contexts">Contexts in which this element can be used</span>:</dt>
    <dd>As a child of an <code>hgroup</code> element.</dd>
-   <dd>Where <span>flow content</span> is expected.</dd>
+   <dd>Where <span>flow content</span> or <span>heading content</span> is expected.</dd>
    <dt><span data-x="concept-element-content-model">Content model</span>:</dt>
    <dd><span>Phrasing content</span>.</dd>
    <dt><span data-x="concept-element-attributes">Content attributes</span>:</dt>
@@ -16314,7 +16314,7 @@ interface <dfn>HTMLHeadingElement</dfn> : <span>HTMLElement</span> {
    <dd><span>Heading content</span>.</dd>
    <dd><span>Palpable content</span>.</dd>
    <dt><span data-x="concept-element-contexts">Contexts in which this element can be used</span>:</dt>
-   <dd>Where <span>flow content</span> is expected.</dd>
+   <dd>Where <span>flow content</span> or <span>heading content</span> is expected.</dd>
    <dt><span data-x="concept-element-content-model">Content model</span>:</dt>
    <dd>One or more <code>h1</code>, <code>h2</code>, <code>h3</code>, <code>h4</code>,
    <code>h5</code>, <code>h6</code> elements, optionally intermixed with <span>script-supporting
@@ -53274,6 +53274,31 @@ interface <dfn>HTMLFieldSetElement</dfn> : <span>HTMLElement</span> {
 
   </div>
 
+  <div class="example">
+
+   <p>This example shows a grouping of controls where the <code>legend</code> element both labels
+   the grouping, and the nested heading element surfaces the grouping in the document outline:</p>
+
+   <pre><code class="html" data-x="">&lt;fieldset>
+ &lt;legend> &lt;h2>
+  How can we best reach you?
+ &lt;/h2> &lt;/legend>
+ &lt;p> &lt;label>
+ &lt;input type=radio checked name=contact_pref>
+  Phone
+ &lt;/label> &lt;/p>
+ &lt;p> &lt;label>
+  &lt;input type=radio name=contact_pref>
+  Text
+ &lt;/label> &lt;/p>
+ &lt;p> &lt;label>
+  &lt;input type=radio name=contact_pref>
+  Email
+ &lt;/label> &lt;/p>
+&lt;/fieldset></code></pre>
+
+  </div>
+
 
   <h4>The <dfn><code>legend</code></dfn> element</h4>
 
@@ -53283,7 +53308,7 @@ interface <dfn>HTMLFieldSetElement</dfn> : <span>HTMLElement</span> {
    <dt><span data-x="concept-element-contexts">Contexts in which this element can be used</span>:</dt>
    <dd>As the <span>first child</span> of a <code>fieldset</code> element.</dd>
    <dt><span data-x="concept-element-content-model">Content model</span>:</dt>
-   <dd><span>Phrasing content</span>.</dd>
+   <dd><span>Phrasing content</span>, optionally intermixed with <span>heading content</span>.</dd>
    <dt><span data-x="concept-element-attributes">Content attributes</span>:</dt>
    <dd><span>Global attributes</span></dd>
    <dt><span
@@ -57950,8 +57975,7 @@ interface <dfn>HTMLDetailsElement</dfn> : <span>HTMLElement</span> {
    <dt><span data-x="concept-element-contexts">Contexts in which this element can be used</span>:</dt>
    <dd>As the <span>first child</span> of a <code>details</code> element.</dd>
    <dt><span data-x="concept-element-content-model">Content model</span>:</dt>
-   <dd>Either: <span>phrasing content</span>.</dd>
-   <dd>Or: one element of <span>heading content</span>.</dd>
+   <dd><span>Phrasing content</span>, optionally intermixed with <span>heading content</span>.</dd>
    <dt><span data-x="concept-element-attributes">Content attributes</span>:</dt>
    <dd><span>Global attributes</span></dd>
    <dt><span
@@ -120608,7 +120632,8 @@ interface <dfn>External</dfn> {
      <td><span data-x="Flow content">flow</span>;
          <span data-x="Heading content">heading</span>;
          <span data-x="Palpable content">palpable</span></td>
-     <td><code>hgroup</code>;
+     <td><code>legend</code>;
+         <code>summary</code>;
          <span data-x="Flow content">flow</span></td>
      <td><span data-x="Phrasing content">phrasing</span></td>
      <td><span data-x="global attributes">globals</span></td>
@@ -120642,7 +120667,10 @@ interface <dfn>External</dfn> {
      <td><span data-x="Flow content">flow</span>;
          <span data-x="Heading content">heading</span>;
          <span data-x="Palpable content">palpable</span></td>
-     <td><span data-x="Flow content">flow</span></td>
+     <td>
+      <code>legend</code>;
+      <code>summary</code>;
+      <span data-x="Flow content">flow</span></td>
      <td><code>h1</code>;
          <code>h2</code>;
          <code>h3</code>;
@@ -120833,7 +120861,8 @@ interface <dfn>External</dfn> {
      <td>Caption for <code>fieldset</code></td>
      <td>none</td>
      <td><code>fieldset</code></td>
-     <td><span data-x="Phrasing content">phrasing</span></td>
+     <td><span data-x="Phrasing content">phrasing</span>;
+         <span data-x="heading content">heading content</span></td>
      <td><span data-x="global attributes">globals</span></td>
      <td><code>HTMLLegendElement</code></td>
     </tr>
@@ -121378,7 +121407,8 @@ interface <dfn>External</dfn> {
      <td>Caption for <code>details</code></td>
      <td>none</td>
      <td><code>details</code></td>
-     <td><span data-x="Phrasing content">phrasing</span></td>
+     <td><span data-x="Phrasing content">phrasing</span>;
+         <span data-x="Heading content">heading content</span></td>
      <td><span data-x="global attributes">globals</span></td>
      <td><code>HTMLElement</code></td>
     </tr>