Allow mocking SendSideCongestionController for Call tests.

webrtc/modules/congestion_controller/include/send_side_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 39 matching lines @@
   class Observer {
    public:
     virtual void OnNetworkChanged(uint32_t bitrate_bps,
                                   uint8_t fraction_loss,  // 0 - 255.
                                   int64_t rtt_ms,
                                   int64_t probing_interval_ms) = 0;
 
    protected:
     virtual ~Observer() {}
   };
-  // TODO(nisse): Consider deleting the |observer| argument to constructors.
+  // TODO(nisse): Consider deleting the |observer| argument to constructors
+  // once CongestionController is deleted.
   SendSideCongestionController(const Clock* clock,
                                Observer* observer,
                                RtcEventLog* event_log,
                                PacketRouter* packet_router);
   SendSideCongestionController(const Clock* clock,
                                Observer* observer,
                                RtcEventLog* event_log,
                                std::unique_ptr<PacedSender> pacer);
   virtual ~SendSideCongestionController();
 
@@ skipping 83 matching lines @@
   std::unique_ptr<DelayBasedBwe> delay_based_bwe_ GUARDED_BY(bwe_lock_);
 
   rtc::ThreadChecker worker_thread_checker_;
 
   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(SendSideCongestionController);
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_CONGESTION_CONTROLLER_INCLUDE_SEND_SIDE_CONGESTION_CONTROLLER_H_