Revert of Remove unnecessary interface TelephoneEventHandler

webrtc/voice_engine/channel.cc

Index: webrtc/voice_engine/channel.cc
diff --git a/webrtc/voice_engine/channel.cc b/webrtc/voice_engine/channel.cc
index 7895e9b9e142a283c311730d953f03e06687c2db..582bde5f26216f645340ef2102d87e485ff2fafb 100644
--- a/webrtc/voice_engine/channel.cc
+++ b/webrtc/voice_engine/channel.cc
@@ -809,6 +809,7 @@
                                            this,
                                            this,
                                            rtp_payload_registry_.get())),
+      telephone_event_handler_(rtp_receiver_->GetTelephoneEventHandler()),
       _outputAudioLevel(),
       _externalTransport(false),
       // Avoid conflict with other channels by adding 1024 - 1026,
@@ -978,6 +979,7 @@
   // disabled by the user.
   // After StopListen (when no sockets exists), RTCP packets will no longer
   // be transmitted since the Transport object will then be invalid.
+  telephone_event_handler_->SetTelephoneEventForwardToDecoder(true);
   // RTCP is enabled by default.
   _rtpRtcpModule->SetRTCPStatus(RtcpMode::kCompound);
   // --- Register all permanent callbacks