fix(webvitals): Use browserPerformanceTimeOrigin for web vitals timestamps

Author: dashed

packages/tracing/src/browser/metrics.ts

@@ -236,11 +236,13 @@ export class MetricsInstrumentation {
         return;
       }
 
-      const timeOrigin = msToSec(performance.timeOrigin);
       const startTime = msToSec(entry.startTime as number);
       logger.log('[Measurements] Adding LCP');
       this._measurements['lcp'] = { value: metric.value };
-      this._measurements['mark.lcp'] = { value: timeOrigin + startTime };
+      if (browserPerformanceTimeOrigin !== undefined) {
+        const timeOrigin = msToSec(browserPerformanceTimeOrigin);
+        this._measurements['mark.lcp'] = { value: timeOrigin + startTime };
+      }
     });
   }
 
@@ -253,11 +255,13 @@ export class MetricsInstrumentation {
         return;
       }
 
-      const timeOrigin = msToSec(performance.timeOrigin);
       const startTime = msToSec(entry.startTime as number);
       logger.log('[Measurements] Adding FID');
       this._measurements['fid'] = { value: metric.value };
-      this._measurements['mark.fid'] = { value: timeOrigin + startTime };
+      if (browserPerformanceTimeOrigin !== undefined) {
+        const timeOrigin = msToSec(browserPerformanceTimeOrigin);
+        this._measurements['mark.fid'] = { value: timeOrigin + startTime };
+      }
     });
   }