Get rid of unnecessary cast of FlexfecReceiveStreamImpl to FlexfecReceiveStream

webrtc/call/flexfec_receive_stream_impl.cc

 /*
  *  Copyright (c) 2016 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 188 matching lines @@
   rtc::CritScope cs(&crit_);
   started_ = false;
 }
 
 // TODO(brandtr): Implement this member function when we have designed the
 // stats for FlexFEC.
 FlexfecReceiveStreamImpl::Stats FlexfecReceiveStreamImpl::GetStats() const {
   return FlexfecReceiveStream::Stats();
 }
 
+const FlexfecReceiveStream::Config& FlexfecReceiveStreamImpl::GetConfig()
+    const {
+  return config_;
+}
+
 }  // namespace webrtc