Change WebRTC SslCipher to be exposed as number only.

webrtc/p2p/base/p2ptransportchannel.h

Index: webrtc/p2p/base/p2ptransportchannel.h
diff --git a/webrtc/p2p/base/p2ptransportchannel.h b/webrtc/p2p/base/p2ptransportchannel.h
index a8f16666c9625897de4cff8e9f0e11a86c76d13e..571cbd96d2bb260151a99e53811b64605156318d 100644
--- a/webrtc/p2p/base/p2ptransportchannel.h
+++ b/webrtc/p2p/base/p2ptransportchannel.h
@@ -115,9 +115,7 @@ class P2PTransportChannel : public TransportChannelImpl,
   }
 
   // Find out which DTLS cipher was negotiated.
-  bool GetSslCipher(std::string* cipher) override {
-    return false;
-  }
+  bool GetSslCipher(rtc::SslCipher* cipher) override { return false; }
 
   // Returns null because the channel is not encrypted by default.
   rtc::scoped_refptr<rtc::RTCCertificate> GetLocalCertificate() const override {