Move rtp dump writer from quality test to test transport

webrtc/video/screenshare_loopback.cc

Index: webrtc/video/screenshare_loopback.cc
diff --git a/webrtc/video/screenshare_loopback.cc b/webrtc/video/screenshare_loopback.cc
index d9de841084e3685c62ba01988a43e28c635275c9..c8aa2dc0b89938934e0ef56bc750bdcba9174279 100644
--- a/webrtc/video/screenshare_loopback.cc
+++ b/webrtc/video/screenshare_loopback.cc
@@ -312,8 +312,8 @@ void Loopback() {
 
 int main(int argc, char* argv[]) {
   ::testing::InitGoogleTest(&argc, argv);
-  rtc::FlagList::SetFlagsFromCommandLine(&argc, argv, true);
-  if (webrtc::flags::FLAG_help) {
+  int flag_status = rtc::FlagList::SetFlagsFromCommandLine(&argc, argv, true);
+  if (webrtc::flags::FLAG_help || flag_status > 0) {
     rtc::FlagList::Print(nullptr, false);
     return 0;
   }