Fix hide download toolbar button

Probably a merge problem that you ran into

Auditors: @bridiver

Introduced here: 7280390

It was causing the close button to render wrongly and also failing automated unit tests on the downloads bar

app/renderer/components/downloadsBar.js

@@ -39,7 +39,8 @@ class DownloadsBar extends ImmutableComponent {
         }
       </div>
       <div className='downloadBarButtons'>
-        <Button className='downloadButton'
+        <Button iconClass='fa-times'
+          className='hideDownloadsToolbar downloadButton smallButton hideButton'
           onClick={this.onHideDownloadsToolbar} />
       </div>
     </div>