src/vs/editor/common/viewLayout/viewLayout.ts/ViewLayout/_getHorizontalScrollbarHeight
class ViewLayout:	private _getHorizontalScrollbarHeight(width: number, scrollWidth: number): number {
		const options = this._configuration.options;
		const scrollbar = options.get(EditorOption.scrollbar);
		if (scrollbar.horizontal === ScrollbarVisibility.Hidden) {
			// horizontal scrollbar not visible
			return 0;
		}
		if (width >= scrollWidth) {
			// horizontal scrollbar not visible
			return 0;
		}
		return scrollbar.horizontalScrollbarSize;
	}