[Chromoting] Add debug logging for display select

Change-Id: Ieabbbfa165fd8c66e1a3f672fc1cbf9e1c575117
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1613641
Auto-Submit: Gary Kacmarcik <garykac@chromium.org>
Reviewed-by: Jamie Walch <jamiewalch@chromium.org>
Commit-Queue: Jamie Walch <jamiewalch@chromium.org>
Cr-Commit-Position: refs/heads/master@{#660047}

remoting/host/client_session.cc

@@ -252,6 +252,8 @@ void ClientSession::SelectDesktopDisplay(
       id = webrtc::kFullDesktopScreenId;
     }
   }
+  LOG(INFO) << "SelectDesktopDisplay " << id << " from '" << select_display.id()
+            << "'";
   video_stream_->SelectSource(id);
   show_display_id_ = id;
 }