Add a new GetTlsUniqueChannelBinding method to SSLSocket, and implement nss version.

net/socket/ssl_server_socket_nss.h

Index: net/socket/ssl_server_socket_nss.h
diff --git a/net/socket/ssl_server_socket_nss.h b/net/socket/ssl_server_socket_nss.h
index ba5564958faf355ddf7b2691eb105c5e1e2fb64e..bc4239a9e8f1a38524c7ce50c677bc78ad42f971 100644
--- a/net/socket/ssl_server_socket_nss.h
+++ b/net/socket/ssl_server_socket_nss.h
@@ -32,11 +32,14 @@ class SSLServerSocketNSS : public SSLServerSocket {
 
   // SSLServerSocket interface.
   virtual int Handshake(const CompletionCallback& callback) OVERRIDE;
+
+  // SSLSocket interface.
   virtual int ExportKeyingMaterial(const base::StringPiece& label,
                                    bool has_context,
                                    const base::StringPiece& context,
                                    unsigned char* out,
                                    unsigned int outlen) OVERRIDE;
+  virtual int GetTLSUniqueChannelBinding(std::string* out) OVERRIDE;
 
   // Socket interface (via StreamSocket).
   virtual int Read(IOBuffer* buf, int buf_len,