Wire up send-side bandwidth estimation.

webrtc/video/video_loopback.cc

Index: webrtc/video/video_loopback.cc
diff --git a/webrtc/video/video_loopback.cc b/webrtc/video/video_loopback.cc
index 789b5cceacf0f4601a7c391bc7590c069b3cce16..ba08197e54fb1108cf56b0a15b42cbe993f6eafa 100644
--- a/webrtc/video/video_loopback.cc
+++ b/webrtc/video/video_loopback.cc
@@ -112,6 +112,7 @@ size_t NumTemporalLayers() {
   return static_cast<size_t>(FLAGS_num_temporal_layers);
 }
 
+DEFINE_bool(send_side_bwe, false, "Use send-side bandwidth estimation");
 }  // namespace flags
 
 void Loopback() {
@@ -129,7 +130,8 @@ void Loopback() {
                                 flags::QueueSize(),
                                 flags::AvgPropagationDelayMs(),
                                 flags::StdPropagationDelayMs(),
-                                flags::FLAGS_logs};
+                                flags::FLAGS_logs,
+                                flags::FLAGS_send_side_bwe};
   test::Loopback loopback(config);
   loopback.Run();
 }