src/vs/base/browser/ui/progressbar/progressbar.ts/ProgressBar/constructor
class ProgressBar:	constructor(container: HTMLElement, options?: IProgressBarOptions) {
		super();

		this.options = options || Object.create(null);
		mixin(this.options, defaultOpts, false);

		this.workedVal = 0;

		this.progressBarBackground = this.options.progressBarBackground;

		this._register(this.showDelayedScheduler = new RunOnceScheduler(() => show(this.element), 0));

		this.create(container);
	}