perfetto: Revert exporting to atrace when tracing using perfetto

Our webview startup benchmark gets confused if we export to atrace,
because it is tracing both via atrace and chrome. If we export
correctly to atrace, we end up with duplicate events in chrome.

Before my recent begin/end split patch, we only exported END events
to atrace, which were pretty meaningless on their own. This patch
essentially restores the behavior prior to my patch by not exporting
any events to atrace when perfetto tracing is enabled.

Long term, we have to figure out how to prevent the duplicate events
in our benchmarks.

Bug: 1028882
Change-Id: If2595ad4d7f46c37a7bbc464d7fd71ad129d0923
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1939748
Auto-Submit: Eric Seckler <eseckler@chromium.org>
Reviewed-by: Stephen Nusko <nuskos@chromium.org>
Commit-Queue: Eric Seckler <eseckler@chromium.org>
Cr-Commit-Position: refs/heads/master@{#719590}

services/tracing/public/cpp/perfetto/track_event_thread_local_event_sink.cc

@@ -535,14 +535,6 @@ void TrackEventThreadLocalEventSink::PrepareTrackEvent(
     interned_source_locations_.Clear();
     interned_log_message_bodies_.Clear();
   }
-
-#if defined(OS_ANDROID)
-  // Send the original trace event to atrace. Since we send COMPLETE events,
-  // make sure not to send the END events that were split from a COMPLETE event.
-  if (!is_end_of_a_complete_event) {
-    trace_event->SendToATrace();
-  }
-#endif
 }
 
 void TrackEventThreadLocalEventSink::EmitStoredInternedData(