Update description of BufferUpdater class
Update description of BufferUpdater class

alechenninger/dartlang,agudulin/dartlang,thso/dartlang,xxgreg/dartlang,alechenninger/dartlang,thso/dartlang,dart-atom/dartlang,dart-atom/dartlang,agudulin/dartlang,xxgreg/dartlang,alechenninger/dartlang,agudulin/dartlang,xxgreg/dartlang,thso/dartlang