Allow mocking SendSideCongestionController for Call tests.

webrtc/modules/congestion_controller/include/congestion_controller.h

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 32 matching lines @@
 class RemoteBitrateObserver;
 class RtcEventLog;
 
 class CongestionController : public CallStatsObserver,
                              public Module,
                              public TransportFeedbackObserver {
  public:
   using Observer = SendSideCongestionController::Observer;
 
   CongestionController(const Clock* clock,
-                       Observer* observer,
+                       Observer* /* observer */,

[nisse-webrtc, 2017/04/26 07:37:14]

I think it's best to keep this argument. We plan to delete this all-in-one class
fairly soon, in favor of the receive side and send side classes, but it's kept
for now to not break downstream projects. 

[Zach Stein, 2017/04/26 20:39:53]

What downstream projects might this break? I'm not seeing anything worrying in
code search, but I might not be looking in the right places. Or perhaps this is
more public than I am assuming?

                        RemoteBitrateObserver* /* remote_bitrate_observer */,
                        RtcEventLog* event_log,
                        PacketRouter* packet_router)
-      : send_side_cc_(clock, observer, event_log, packet_router),
+      : send_side_cc_(clock, event_log, packet_router),
         receive_side_cc_(clock, packet_router) {}
   CongestionController(const Clock* clock,
-                       Observer* observer,
-                       RemoteBitrateObserver* remote_bitrate_observer,
+                       Observer* /* observer */,
+                       RemoteBitrateObserver* /* remote_bitrate_observer */,
                        RtcEventLog* event_log,
                        PacketRouter* packet_router,
                        std::unique_ptr<PacedSender> pacer)
-      : send_side_cc_(clock, observer, event_log, std::move(pacer)),
+      : send_side_cc_(clock, event_log, std::move(pacer)),
         receive_side_cc_(clock, packet_router) {}
 
   virtual ~CongestionController() {}
 
   virtual void OnReceivedPacket(int64_t arrival_time_ms,
                                 size_t payload_size,
                                 const RTPHeader& header);
 
   virtual void SetBweBitrates(int min_bitrate_bps,
                               int start_bitrate_bps,
@@ skipping 56 matching lines @@
  private:
   SendSideCongestionController send_side_cc_;
   ReceiveSideCongestionController receive_side_cc_;
 
   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(CongestionController);
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_CONGESTION_CONTROLLER_INCLUDE_CONGESTION_CONTROLLER_H_