src/vs/workbench/browser/parts/banner/bannerPart.ts/BannerPart/close
class BannerPart:	private close(item: IBannerItem): void {
		// Hide banner
		this.setVisibility(false);

		// Remove from document
		clearNode(this.element);

		// Remember choice
		if (typeof item.onClose === 'function') {
			item.onClose();
		}

		this.item = undefined;
	}