src/vs/workbench/browser/parts/editor/tabsTitleControl.ts/TabsTitleControl/getTabAndIndex
class TabsTitleControl:	private getTabAndIndex(editor: IEditorInput): [HTMLElement, number /* index */] | undefined {
		const editorIndex = this.group.getIndexOfEditor(editor);
		const tab = this.getTabAtIndex(editorIndex);
		if (tab) {
			return [tab, editorIndex];
		}

		return undefined;
	}