Cache performanceNow method

Summary: Changelog: [Internal]

Reviewed By: lenaic

Differential Revision: D72410946

fbshipit-source-id: 7097e7bf6ac613adccce7fe1267fb70785f976b3

packages/react-native/Libraries/__tests__/__snapshots__/public-api-test.js.snap

@@ -9863,7 +9863,7 @@ declare export default class Performance {
     endMark?: string
   ): PerformanceMeasure;
   clearMeasures(measureName?: string): void;
-  now(): DOMHighResTimeStamp;
+  now: () => DOMHighResTimeStamp;
   getEntries(): PerformanceEntryList;
   getEntriesByType(entryType: PerformanceEntryType): PerformanceEntryList;
   getEntriesByName(

packages/react-native/src/private/webapis/performance/Performance.js

@@ -226,9 +226,7 @@ export default class Performance {
    * Returns a double, measured in milliseconds.
    * https://developer.mozilla.org/en-US/docs/Web/API/Performance/now
    */
-  now(): DOMHighResTimeStamp {
-    return getCurrentTimeStamp();
-  }
+  now: () => DOMHighResTimeStamp = getCurrentTimeStamp;
 
   /**
    * An extension that allows to get back to JS all currently logged marks/measures