Tail BR is removed from end of block

[Garry Yao]

This's derived from #205.

Reproducing Procedures

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

   <div><h5>title</h5><br /></div>line
   

3. Switch to wsiwyg and switch back to 'source';
   • Actual Result:

     <div>
     	<h5>
     		title</h5>
     </div>
     <p>
     	line</p>
     

   • Expected Result: The origianl source remains the same.

[Garry Yao]

It's not a bug, block tail <br> within 'source' mode has no visual effect so is trimmed.