Define remainder of insertAdjacentElement()

It needs to actually return something and rethrow exceptions in all
cases.

Also add a note to indicate insertAdjacentText() does not return
anything.

Per feedback from Olli on #whatwg IRC.

dom.bs

@@ -5586,7 +5586,7 @@ steps:
  <li><p>Let <var>qualifiedName</var> be <a>context object</a>'s <a for=Element>qualified name</a>.
 
  <li><p>If the <a>context object</a> is in the <a>HTML namespace</a> and its <a>node document</a> is
- an <a>HTML document</a>, let <var>qualifiedName</var> be <span>converted to ASCII uppercase</span>.
+ an <a>HTML document</a>, let <var>qualifiedName</var> be <a>converted to ASCII uppercase</a>.
 
  <li>Return <var>qualifiedName</var>.
 </ol>
@@ -5930,22 +5930,23 @@ for the <a>context object</a>.
  <dd>
   <p>If <var>element</var>'s <a>parent</a> is null, return null.
 
-  <p><a for=Node>Pre-insert</a> <var>node</var> into <var>element</var>'s <a>parent</a> before
-  <var>element</var>. Rethrow any exceptions.
+  <p>Return the result of <a for=Node>pre-inserting</a> <var>node</var> into <var>element</var>'s
+  <a>parent</a> before <var>element</var>. Rethrow any exceptions.
 
  <dt>"<code>afterbegin</code>"
- <dd><p><a for=Node>Pre-insert</a> <var>node</var> into <var>element</var> before
- <var>element</var>'s <a for=tree>first child</a>.
+ <dd><p>Return the result of <a for=Node>pre-inserting</a> <var>node</var> into <var>element</var>
+ before <var>element</var>'s <a for=tree>first child</a>. Rethrow any exceptions.
 
  <dt>"<code>beforeend</code>"
- <dd><p><a for=Node>Pre-insert</a> <var>node</var> into <var>element</var> before null.
+ <dd><p>Return the result of <a for=Node>pre-inserting</a> <var>node</var> into <var>element</var>
+ before null. Rethrow any exceptions.
 
  <dt>"<code>afterend</code>"
  <dd>
   <p>If <var>element</var>'s <a>parent</a> is null, return null.
 
-  <p><a for=Node>Pre-insert</a> <var>node</var> into <var>element</var>'s <a>parent</a> before
-  <var>element</var>'s <a for=tree>next sibling</a>. Rethrow any exceptions.
+  <p>Return the result of <a for=Node>pre-inserting</a> <var>node</var> into <var>element</var>'s
+  <a>parent</a> before <var>element</var>'s <a for=tree>next sibling</a>. Rethrow any exceptions.
 
  <dt>Otherwise</dt>
  <dd><p>Throw a {{SyntaxError}} exception.
@@ -5967,6 +5968,8 @@ method, when invoked, must run these steps:
  <var>text</var>. Rethrow any exceptions.
 </ol>
 
+<p class="note">This method returns nothing because it existed before we had a chance to design it.
+
 
 <h4 id='interface-namednodemap'>Interface {{NamedNodeMap}}</h4>