testPrepareContent() {
    setUpFields(true);
    assertPreparedContents('hi', 'hi');
    assertPreparedContents(
        BrowserFeature.COLLAPSES_EMPTY_NODES ? '<br>' : '', '   ');
  }
Tests that deleteCursorSelectionW3C_ correctly recognizes visually
collapsed selections in Opera even if they contain a <br>.
See the deleteCursorSelectionW3C_ comment in enterhandler.js.