Track number of loaded plugins

Reviewed By: lblasa

Differential Revision: D50556872

fbshipit-source-id: 2d841360f7081074afa025d0bad8c41d7b2db16e

desktop/flipper-ui-core/src/startFlipperDesktop.tsx

@@ -162,7 +162,11 @@ function init(flipperServer: FlipperServer) {
     // We could potentially merge ui-perf-store-rehydrated and ui-perf-everything-finally-loaded-jeeeez,
     // but what if at some point in the future we relalize that store rehydration is not actually the last event?
     // Keep it separate for the time being (evil laugh as there is nothing more permanent than temporary stuff)
-    uiPerfTracker.track('ui-perf-everything-finally-loaded-jeeeez');
+    uiPerfTracker.track('ui-perf-everything-finally-loaded-jeeeez', {
+      numberOfPlugins:
+        store.getState().plugins.clientPlugins.size +
+        store.getState().plugins.devicePlugins.size,
+    });
   });
 
   setPersistor(persistor);

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

@@ -22,10 +22,11 @@ class UIPerfTracker {
     this.t0 = performance.now();
   }
 
-  track(event: UIPerfEvents) {
+  track(event: UIPerfEvents, data?: any) {
     const tx = performance.now();
     getLogger().track('performance', event, {
       time: tx - this.t0,
+      data,
     });
   }
 }