anchor.diff:  /// ## Class BoneAnimation
   /// represents Key frame animation data for a single bone in a skeleton.
   class BoneAnimation {
  -  final int boneIndex;
  +  final Bone bone;
   
     List<double> _positionTimes;
     List<VM.Vector3> _positionValues;
  
positive.code:   /// Construct bone animation with [boneName]. Animation key frames
    /// will be loaded from [positions], [rotations], and [scales].
    BoneAnimation(
        this.boneIndex,
        this._positionTimes,
        this._positionValues,
        this._rotationTimes,
  
negative.code:     VM.Quaternion r = _rotationValues[rotationIndex];
      boneMatrix.setFromTranslationRotationScale(t, r, s);
    }
  
    @override
    String toString() {
      List<String> s = [];
      //s.add("${bone.boneName} [${bone.boneIndex}]");
      s.add("${bone.boneName}");
      s.add("${_positionTimes.length}: ${_positionValues}");
      s.add("${_rotationTimes.length}: ${_rotationValues}");
      s.add("${_scaleTimes.length}: ${_scaleValues}");
      return s.join("\n");
    }
  }
  
  /// ## Class SkeletalAnimation
  