src/vs/base/browser/ui/button/button.ts/ButtonBar/pushButton
class ButtonBar:	private pushButton(button: IButton): void {
		this._buttons.push(button);

		const index = this._buttons.length - 1;
		this._register(addDisposableListener(button.element, EventType.KEY_DOWN, e => {
			const event = new StandardKeyboardEvent(e);
			let eventHandled = true;

			// Next / Previous Button
			let buttonIndexToFocus: number | undefined;
			if (event.equals(KeyCode.LeftArrow)) {
				buttonIndexToFocus = index > 0 ? index - 1 : this._buttons.length - 1;
			} else if (event.equals(KeyCode.RightArrow)) {
				buttonIndexToFocus = index === this._buttons.length - 1 ? 0 : index + 1;
			} else {
				eventHandled = false;
			}

			if (eventHandled && typeof buttonIndexToFocus === 'number') {
				this._buttons[buttonIndexToFocus].focus();
				EventHelper.stop(e, true);
			}

		}));

	}