third_party/WebKit/LayoutTests/editing/deleting/merge-different-styles.html

<script>
if (window.testRunner)
     testRunner.dumpEditingCallbacks();
</script>
<p>This places the caret before the 'b' in 'bar' and Deletes.  'foo' and 'bar' should end up on the same line, but neither should change style.</p>
<div contenteditable="true">
<div>foo</div>
<div id="test" style="font-weight:bold">bar</div>
</div>

<script>
var s = window.getSelection();
var e = document.getElementById("test");
s.collapse(e, 0);
document.execCommand("Delete");
</script>