fix warning

src/vs/workbench/browser/layout.ts

@@ -25,7 +25,6 @@ import { SidebarPart } from 'vs/workbench/browser/parts/sidebar/sidebarPart';
 import { PanelPart } from 'vs/workbench/browser/parts/panel/panelPart';
 import { StatusbarPart } from 'vs/workbench/browser/parts/statusbar/statusbarPart';
 import { getZoomFactor } from 'vs/base/browser/browser';
-import * as perf from 'vs/base/common/performance';
 
 const TITLE_BAR_HEIGHT = isMacintosh ? 22 : 30;
 const STATUS_BAR_HEIGHT = 22;