I googled but couldn't find an answer.
Is there a cross-browser compatibility matrix available for this feature?
In case anybody wants to know the answer, here it is: Mutation Observers vs Mutation Events/Browser Availability.
This feature (DOM mutation) is working from Chrome 18. You can see more details here: http://updates.html5rocks.com/2012/02/Detect-DOM-changes-with-Mutation-Observers
In case you wish to check 'any' HTML5 feature and the browsers that support it: http://caniuse.com/ is the place. Other great source is: http://html5please.com/