constructor(overridingOptions = {}) {
    this.options_ = new Options(this.defaultOptions());
    this.options_.setFromObject(overridingOptions);
    // Only used if this.options_.sourceMaps is set.
    this.sourceMapConfiguration_ = null;
    // Only used if this.options_sourceMaps = 'memory'.
    this.sourceMapInfo_ = null;
    // Used to cache source map calculation
    this.sourceMapCache_ = null;
  }
Synchronous source to source compiler using default values for options.
@param {Options=} overridingOptions