Added video freezing / roughness trace events.

This lets us record the events in telemetry.

Change-Id: I90348045cdca95705be99b5900376fd6e13577d5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2441018Reviewed-by: Eugene Zemtsov <eugene@chromium.org>
Commit-Queue: Frank Liberato <liberato@chromium.org>
Cr-Commit-Position: refs/heads/master@{#836809}

content/renderer/media/media_factory.cc

@@ -193,6 +193,11 @@ void LogRoughness(
     // score we want.  For now, don't record anything so we don't have a mis-
     // match of UMA values.
   }
+
+  TRACE_EVENT2("media", "VideoPlaybackRoughness", "id", media_log->id(),
+               "roughness", measurement.roughness);
+  TRACE_EVENT2("media", "VideoPlaybackFreezing", "id", media_log->id(),
+               "freezing", measurement.freezing.InMilliseconds());
 }
 
 std::unique_ptr<media::DefaultRendererFactory> CreateDefaultRendererFactory(