Add trace events to check thread priority in RealtimeAudioWorkletThread

The Finch setting might not be activated for some cases, and we want to
provide developers with thread priority information via chrome://tracing.

Bug: 1165842
Change-Id: I50cf618587acb8ce01237c894a21ad4965e22a62
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2631288Reviewed-by: Raymond Toy <rtoy@chromium.org>
Auto-Submit: Hongchan Choi <hongchan@chromium.org>
Commit-Queue: Hongchan Choi <hongchan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#844124}

third_party/blink/renderer/modules/webaudio/realtime_audio_worklet_thread.cc

@@ -32,8 +32,12 @@ RealtimeAudioWorkletThread::RealtimeAudioWorkletThread(
     // TODO(crbug.com/1022888): The worklet thread priority is always NORMAL on
     // Linux and Chrome OS regardless of this thread priority setting.
     params.thread_priority = base::ThreadPriority::REALTIME_AUDIO;
+    TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("audio-worklet"),
+                 "RealtimeAudioWorkletThread() - REALTIME_AUDIO");
   } else {
     params.thread_priority = base::ThreadPriority::NORMAL;
+    TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("audio-worklet"),
+                 "RealtimeAudioWorkletThread() - NORMAL");
   }
 
   if (++s_ref_count_ == 1)