message: ref(apm): Simplify Tracing._addOffsetToSpan
diff: @@ -322,7 +322,7 @@ export class Tracing implements Integration {
  );
  Tracing._activeTransaction = span;
  - Tracing._addOffsetToSpan(`idleTransactionStarted-${Tracing._currentIndex}`, span as SpanClass);
  + Tracing._addOffsetToSpan(span as SpanClass);
  // We need to do this workaround here and not use configureScope
  // Reason being at the time we start the inital transaction we do not have a client bound on the hub yet
  @@ -543,15 +543,9 @@ export class Tracing implements Integration {
  * @param measureName name of the performance measure
  * @param span Span to add data.offset to
  */
  - private static _addOffsetToSpan(measureName: string, span: SpanClass): void {
  + private static _addOffsetToSpan(span: SpanClass): void {
  if (global.performance) {
  - const name = `#sentry-${measureName}`;
  - performance.measure(name);
  - const measure = performance.getEntriesByName(name).pop();
  - if (measure) {
  - span.setData('offset', Tracing._msToSec(measure.duration));
  - }
  - performance.clearMeasures(name);
  + span.setData('offset', Tracing._msToSec(performance.now()));
  }
  }
  @@ -594,7 +588,7 @@ export class Tracing implements Integration {
  const hub = _getCurrentHub();
  if (hub) {
  const span = hub.startSpan(spanContext);
  - Tracing._addOffsetToSpan(`${name}${Tracing._currentIndex}`, span as SpanClass);
  + Tracing._addOffsetToSpan(span as SpanClass);
  Tracing._activities[Tracing._currentIndex] = {
  name,
  span,
  