Revert "Revert of Parse FlexFEC RTP headers in Call and add integration with BWE. (patchset #17 id:460001 of https://codereview.webrtc.org/2553863003/ )"

Problem fixed: RTP header extensions were not properly set in tests.

BUG=webrtc:5654

Review-Url: https://codereview.webrtc.org/2593963003
Cr-Commit-Position: refs/heads/master@{#15741}

webrtc/modules/congestion_controller/include/congestion_controller.h

@@ -68,6 +68,10 @@ class CongestionController : public CallStatsObserver, public Module {
                        std::unique_ptr<PacedSender> pacer);
   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,
                               int max_bitrate_bps);