function DataSourceClock() {
  this._definitionChanged = new Event();
  this._startTime = undefined;
  this._stopTime = undefined;
  this._currentTime = undefined;
  this._clockRange = undefined;
  this._clockStep = undefined;
  this._multiplier = undefined;
}
Represents desired clock settings for a particular {@link DataSource}.  These settings may be applied
to the {@link Clock} when the DataSource is loaded.

@alias DataSourceClock
@constructor