[AudioService] Set log factory upon audio process startup.

This fixes a bug where some of the logging from the audio process is not
forwarded to chrome://media-internals.

Fixed: 1049114
Change-Id: I958e47557ba9b6bdc9c9d3e8352994bc140ffb3c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2037677
Commit-Queue: Guido Urdaneta <guidou@chromium.org>
Commit-Queue: Ken Rockot <rockot@google.com>
Auto-Submit: Guido Urdaneta <guidou@chromium.org>
Reviewed-by: Ken Rockot <rockot@google.com>
Cr-Commit-Position: refs/heads/master@{#738676}

content/browser/renderer_host/media/audio_service_listener.cc

@@ -118,6 +118,7 @@ void AudioServiceListener::OnServiceProcessLaunched(
   process_id_ = info.pid;
   metrics_.ServiceCreated();
   metrics_.ServiceStarted();
+  MaybeSetLogFactory();
 }
 
 void AudioServiceListener::OnServiceProcessTerminatedNormally(