new Google Docs is totally different for everything else like tinyMCE, ckEditor and similars. Here is an article describing some of the technologies behind it : http://news.softpedia.com/news/Google-Details-the-Powerful-Technology-Behind-the-New-Docs-Editor-141804.shtml
quoted from the article: “To get around these problems, the new Google document editor doesn’t use the browser to handle editable text. We wrote a brand new editing surface and layout engine, entirely in JavaScript,” Jeff Harris, product manager, Google Docs.
It's amazing how there isn't any open source implementation and people are not aware of this.
The short answer is that they implemented every single logic that a graphic text editor would do, in plain javascript (from layout, to rendering, to everything else)
