src/vs/base/browser/ui/splitview/paneview.ts/PaneView/focusNext
class PaneView:	private focusNext(): void {
		const headers = this.getPaneHeaderElements();
		const index = headers.indexOf(document.activeElement as HTMLElement);

		if (index === -1) {
			return;
		}

		headers[Math.min(index + 1, headers.length - 1)].focus();
	}