[IE] Enter key before sub list result incorrect

[Garry Yao]

This is derived from #1420.

Reproducing Procedures

1. Open the 'replace by class' sample page.
2. Load the document with following content:

      <ol>
   	<li>
   		item1^
   		<ol>
   			<li>
   				item2</li>
   		</ol>
   	</li>
      </ol>
   

3. Press enter key at the caret position;
   • Actual Result in IE: The new list is created, but the line height is not maintained.
   • Actual Result in Firefox: The cursor is still at the end of item 1 with the new list item created.

[Garry Yao]

Affect Firefox.