Track render of sandy container

Reviewed By: lblasa

Differential Revision: D50121105

fbshipit-source-id: 0aa74afe1da069fa28bdd3cf26df8e0cbcefd320

desktop/flipper-ui-core/src/sandy-chrome/SandyApp.tsx

@@ -40,6 +40,7 @@ import {isFBEmployee} from '../utils/fbEmployee';
 import {notification} from 'antd';
 import isProduction from '../utils/isProduction';
 import {getRenderHostInstance} from 'flipper-frontend-core';
+import {uiPerfTracker} from '../utils/UIPerfTracker';
 
 export function SandyApp() {
   const logger = useLogger();
@@ -54,6 +55,7 @@ export function SandyApp() {
     })`;
 
     registerStartupTime(logger);
+    uiPerfTracker.track('ui-perf-sandy-container-rendered');
 
     if (hasPlatformWizardBeenDone(window.localStorage)) {
       Dialog.showModal((onHide) => (

desktop/flipper-ui-core/src/utils/UIPerfTracker.tsx

@@ -12,6 +12,7 @@ import {getLogger} from 'flipper-common';
 type UIPerfEvents =
   | 'ui-perf-store-rehydrated'
   | 'ui-perf-root-rendered'
+  | 'ui-perf-sandy-container-rendered'
   | 'ui-perf-everything-finally-loaded-jeeeez';
 
 class UIPerfTracker {