src/vs/workbench/services/history/browser/historyService.ts/HistoryService/handleEditorCloseEventInHistory
class HistoryService:	private handleEditorCloseEventInHistory(e: IEditorCloseEvent): void {
		const editors = this.editorScopedNavigationStacks.get(e.groupId);
		if (editors) {
			const editorStack = editors.get(e.editor);
			if (editorStack) {
				editorStack.disposable.dispose();
				editors.delete(e.editor);
			}

			if (editors.size === 0) {
				this.editorScopedNavigationStacks.delete(e.groupId);
			}
		}
	}