This issue was originally filed by @seaneagan

The following classes in dart:svg:

AnimatedAngle
AnimatedBoolean
AnimatedEnumeration
AnimatedInteger
AnimatedLength
AnimatedLengthList
AnimatedNumber
AnimatedNumberList
AnimatedPreserveAspectRatio
AnimatedRect
AnimatedString
AnimatedTransformList

could all be replaced by the following interface:

class Animated<T> {
  /// A read only [T] representing the current animated value of the given
  /// attribute. If the given attribute is not currently being animated,
  /// then the [T] will have the same contents as baseVal. The object
  /// referenced by animVal is always distinct from the one referenced
  /// by baseVal, even when the attribute is not animated.
  final T animVal;

  final T baseVal;
}