src/vs/base/browser/ui/selectBox/selectBoxCustom.ts/SelectBoxList/renderSelectDropDown
class SelectBoxList:	private renderSelectDropDown(container: HTMLElement, preLayoutPosition?: boolean): IDisposable {
		container.appendChild(this.selectDropDownContainer);

		// Pre-Layout allows us to change position
		this.layoutSelectDropDown(preLayoutPosition);

		return {
			dispose: () => {
				// contextView will dispose itself if moving from one View to another
				try {
					container.removeChild(this.selectDropDownContainer); // remove to take out the CSS rules we add
				}
				catch (error) {
					// Ignore, removed already by change of focus
				}
			}
		};
	}