Replace TRACE_EVENT_ASYNC* use in UmaPageLoadMetricsObserver

In https://chromium-review.googlesource.com/c/chromium/src/+/2419125 while
moving files there were some presubmit checks failing due to use of
deprecated tracing APIs. This CL fixes this.

Bug: 1038710
Change-Id: I50508b75f1ecc171cab43b9e2c1a7b915d0d8864
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2431447Reviewed-by: Deep Roy <dproy@chromium.org>
Commit-Queue: Nicolás Peña Moreno <npm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#810796}

components/page_load_metrics/browser/observers/core/uma_page_load_metrics_observer.cc

@@ -499,10 +499,10 @@ void UmaPageLoadMetricsObserver::OnFirstContentfulPaintInPage(
     if (timing.paint_timing->first_contentful_paint >
         kFirstContentfulPaintTraceThreshold) {
       base::TimeTicks navigation_start = GetDelegate().GetNavigationStart();
-      TRACE_EVENT_ASYNC_BEGIN_WITH_TIMESTAMP0(
+      TRACE_EVENT_NESTABLE_ASYNC_BEGIN_WITH_TIMESTAMP0(
           "latency", "Long Navigation to First Contentful Paint",
           TRACE_ID_LOCAL(g_num_trace_events_in_process), navigation_start);
-      TRACE_EVENT_ASYNC_END_WITH_TIMESTAMP0(
+      TRACE_EVENT_NESTABLE_ASYNC_END_WITH_TIMESTAMP0(
           "latency", "Long Navigation to First Contentful Paint",
           TRACE_ID_LOCAL(g_num_trace_events_in_process),
           navigation_start +