 The states impacted by this can be limited through <var>owners</var>.</div>
<dl class="notes">
<dt>Parameters:</dt>
<dd><code>owners</code> - Optional set of owners that should be impacted.  If null, all
               undo states will be visible and available for undo.  If non-null, only those
               states that contain one of the owners specified here will be visible.</dd>
<dd><code>count</code> - Number of undo states to pop.</dd>
<dt>Returns:</dt>
<dd>Returns the number of undo states that were