Source
factory MutationObserver(MutationCallback callback) { // Dummy statement to mark types as instantiated. JS('MutationObserver|MutationRecord', '0'); return JS( 'MutationObserver', 'new(window.MutationObserver||window.WebKitMutationObserver||' 'window.MozMutationObserver)(#)', convertDartClosureToJS(_wrapBinaryZone(callback), 2)); }