Fix race in WebRtcVideoEngine2Tests, improve coverage.

webrtc/media/engine/webrtcvideoengine2.cc

Index: webrtc/media/engine/webrtcvideoengine2.cc
diff --git a/webrtc/media/engine/webrtcvideoengine2.cc b/webrtc/media/engine/webrtcvideoengine2.cc
index 8b4c5df1814601757b5d74b80eccf9087c745be5..f48f45c46fd387827f61879c3d2675ec0ca142b8 100644
--- a/webrtc/media/engine/webrtcvideoengine2.cc
+++ b/webrtc/media/engine/webrtcvideoengine2.cc
@@ -1618,6 +1618,9 @@ bool WebRtcVideoChannel2::WebRtcVideoSendStream::SetVideoSend(
       SetCodec(*parameters_.codec_settings, force_encoder_allocation);
       // Mark screenshare parameter as being updated, then test for any other
       // changes that may require codec reconfiguration.
+      // TODO(sprang): Refactor code to guarantee that ReconfigureEncoder is a
+      // subset SetCodec instead, so that we don't unnecessarily reconfigure
+      // the encoder twice.
       old_options.is_screencast = options->is_screencast;
     }
     if (parameters_.options != old_options) {