RichEditableText should support truncation if editing is disabled

Using Label/RichText is fine for truncation until you want text interaction (e.g., selection) and have to use RichEditableText.

One use case is if you wanted to display a URL and truncate after certain width. RichEditableText will wrap the entire text as necessary.

Non-trivial workaround:
http://forums.adobe.com/message/3974420#3974420