Parse FlexFEC RTP headers in Call and add integration with BWE.

webrtc/modules/congestion_controller/congestion_controller.cc

Index: webrtc/modules/congestion_controller/congestion_controller.cc
diff --git a/webrtc/modules/congestion_controller/congestion_controller.cc b/webrtc/modules/congestion_controller/congestion_controller.cc
index c31d441c978ef587dc1968642a7ea6712726ffbe..4a7c40aca03d98698c802df8f601fda5d0392ed9 100644
--- a/webrtc/modules/congestion_controller/congestion_controller.cc
+++ b/webrtc/modules/congestion_controller/congestion_controller.cc
@@ -23,6 +23,7 @@
 #include "webrtc/modules/remote_bitrate_estimator/include/bwe_defines.h"
 #include "webrtc/modules/remote_bitrate_estimator/remote_bitrate_estimator_abs_send_time.h"
 #include "webrtc/modules/remote_bitrate_estimator/remote_bitrate_estimator_single_stream.h"
+#include "webrtc/modules/rtp_rtcp/source/rtp_header_extension.h"
 #include "webrtc/system_wrappers/include/critical_section_wrapper.h"
 
 namespace webrtc {
@@ -274,6 +275,17 @@ void CongestionController::EnablePeriodicAlrProbing(bool enable) {
   probe_controller_->EnablePeriodicAlrProbing(enable);
 }
 
+bool CongestionController::UseSendSideBwe(
+    bool transport_cc,
+    const RtpHeaderExtensionMap& rtp_header_extensions) {
+  // Has the RTCP feedback message been negotiated?
+  if (!transport_cc)
+    return false;
+  // Has the RTP header extension been negotiated?
+  return rtp_header_extensions.IsRegistered(
+      kRtpExtensionTransportSequenceNumber);
+}
+
 void CongestionController::SetAllocatedSendBitrateLimits(
     int min_send_bitrate_bps,
     int max_padding_bitrate_bps) {