Fire slotchange events on the removal and insertion during moveBefore

Author: domfarolino

dom.bs

@@ -2932,6 +2932,13 @@ JavaScript. These steps may queue tasks to do these things asynchronously, howev
 
  <li><p><a for=set>Remove</a> <var>node</var> from <var>oldParent</var>'s <a for=tree>children</a>.
 
+ <li><p>If <var>node</var> is <a for=slottable>assigned</a>, then run <a>assign slottables</a> for
+ <var>node</var>'s <a>assigned slot</a>.
+
+ <li><p>If <var>oldParent</var>'s <a for=tree>root</a> is a <a for=/>shadow root</a>, and
+ <var>oldParent</var> is a <a>slot</a> whose <a for=slot>assigned nodes</a> is the empty list, then
+ run <a>signal a slot change</a> for <var>oldParent</var>.
+
  <!-- Start insertion-related bookkeeping steps -->
  <li>
   <p>If <var>child</var> is non-null: