[editing] The spec about execCommand('indent') in inline block.

Image following HTML ('|' is the caret selection):
<span contenteditable="true" id="span">|text</span>
<script>
document.execCommand('indent', false, null);
</script>

Following current HTML editing, document.execCommand('indent') inserts a
blockquate element inside a span element.
*https://dvcs.w3.org/hg/editing/raw-file/tip/editing.html#indent
<https://dvcs.w3.org/hg/editing/raw-file/tip/editing.html#indent>*
Both Chrome and IE insert a blockquate element inside a span element.
You can try it on:
http://jsfiddle.net/xtk5h/2/

However, the blockquate element is a flow content and HTML standard doesn't
allow flow contents to be contents of a span element:
http://www.whatwg.org/specs/web-apps/current-work/#the-span-element

Which is better we allow indentation in inline element or not?