Google Chrome Dev Channel has an interesting flag named ‘Enable Asynchronous Spellchecking’.
This feature enables the same spell checker that Google Docs now feature. It accesses the same engine for spelling correction that is used by their search engine.
I played around with it enabled and noticed that text areas would large amount of text could slow down the user interface. It does not wait for user interactivity and tries to spell check the entire content.
Google could fine-tune it in the future to make it work only on-demand. Until then, I plan to keep it disabled in my installation.