Add send-side BWE to WebRtcVoiceEngine under a finch experiment.

talk/media/webrtc/webrtcvoiceengine.h

Index: talk/media/webrtc/webrtcvoiceengine.h
diff --git a/talk/media/webrtc/webrtcvoiceengine.h b/talk/media/webrtc/webrtcvoiceengine.h
index ce3bdf3ed70641f78aa8a4ca6fef6433d7018cc8..8f34ee40b794a350c034bc58c835b17877a4bbcc 100644
--- a/talk/media/webrtc/webrtcvoiceengine.h
+++ b/talk/media/webrtc/webrtcvoiceengine.h
@@ -234,9 +234,9 @@ class WebRtcVoiceMediaChannel final : public VoiceMediaChannel,
   WebRtcVoiceEngine* engine() { return engine_; }
   int GetLastEngineError() { return engine()->GetLastEngineError(); }
   int GetOutputLevel(int channel);
-  bool GetRedSendCodec(const AudioCodec& red_codec,
-                       const std::vector<AudioCodec>& all_codecs,
-                       webrtc::CodecInst* send_codec);
+  const AudioCodec* GetRedSendCodec(
+      const AudioCodec& red_codec,
+      const std::vector<AudioCodec>& all_codecs) const;
   bool SetPlayout(int channel, bool playout);
   void SetNack(int channel, bool nack_enabled);
   bool SetSendCodec(int channel, const webrtc::CodecInst& send_codec);
@@ -248,6 +248,9 @@ class WebRtcVoiceMediaChannel final : public VoiceMediaChannel,
   bool IsDefaultRecvStream(uint32_t ssrc) {
     return default_recv_ssrc_ == static_cast<int64_t>(ssrc);
   }
+  const AudioCodec* GetPreferredCodec(const std::vector<AudioCodec>& codecs,
+                                      webrtc::CodecInst* voe_codec,
+                                      int* red_payload_type) const;
   bool SetSendCodecs(int channel, const std::vector<AudioCodec>& codecs);
   bool SetSendBitrateInternal(int bps);
 
@@ -263,6 +266,7 @@ class WebRtcVoiceMediaChannel final : public VoiceMediaChannel,
   rtc::Optional<int> dtmf_payload_type_;
   bool desired_playout_ = false;
   bool nack_enabled_ = false;
+  bool transport_cc_enabled_ = false;
   bool playout_ = false;
   SendFlags desired_send_ = SEND_NOTHING;
   SendFlags send_ = SEND_NOTHING;