Revert of Adding "first packet received" notification to PeerConnectionObserver.

talk/app/webrtc/peerconnectioninterface.h

Index: talk/app/webrtc/peerconnectioninterface.h
diff --git a/talk/app/webrtc/peerconnectioninterface.h b/talk/app/webrtc/peerconnectioninterface.h
index 63faec5ad3d6a3ea3ba7da09b353c4db68454161..b9afbad204ce354a7b3294e1fc9409cae615739b 100644
--- a/talk/app/webrtc/peerconnectioninterface.h
+++ b/talk/app/webrtc/peerconnectioninterface.h
@@ -484,9 +484,6 @@
   // Called when the ICE connection receiving status changes.
   virtual void OnIceConnectionReceivingChange(bool receiving) {}
 
-  // Called when the first RTP packet is received.
-  virtual void OnFirstMediaPacketReceived() {}
-
  protected:
   // Dtor protected as objects shouldn't be deleted via this interface.
   ~PeerConnectionObserver() {}