Revert of Remove unnecessary interface TelephoneEventHandler

webrtc/modules/rtp_rtcp/include/rtp_receiver.h

Index: webrtc/modules/rtp_rtcp/include/rtp_receiver.h
diff --git a/webrtc/modules/rtp_rtcp/include/rtp_receiver.h b/webrtc/modules/rtp_rtcp/include/rtp_receiver.h
index c04a173ff4acafc180053c06ab423a8386610336..9db1c63da78976d554d8530e916f017cf99a66be 100644
--- a/webrtc/modules/rtp_rtcp/include/rtp_receiver.h
+++ b/webrtc/modules/rtp_rtcp/include/rtp_receiver.h
@@ -18,6 +18,21 @@
 
 class RTPPayloadRegistry;
 
+class TelephoneEventHandler {
+ public:
+  virtual ~TelephoneEventHandler() {}
+
+  // The following three methods implement the TelephoneEventHandler interface.
+  // Forward DTMFs to decoder for playout.
+  virtual void SetTelephoneEventForwardToDecoder(bool forward_to_decoder) = 0;
+
+  // Is forwarding of outband telephone events turned on/off?
+  virtual bool TelephoneEventForwardToDecoder() const = 0;
+
+  // Is TelephoneEvent configured with payload type payload_type
+  virtual bool TelephoneEventPayloadType(const int8_t payload_type) const = 0;
+};
+
 class RtpReceiver {
  public:
   // Creates a video-enabled RTP receiver.
@@ -35,6 +50,9 @@
       RTPPayloadRegistry* rtp_payload_registry);
 
   virtual ~RtpReceiver() {}
+
+  // Returns a TelephoneEventHandler if available.
+  virtual TelephoneEventHandler* GetTelephoneEventHandler() = 0;
 
   // Registers a receive payload in the payload registry and notifies the media
   // receiver strategy.