There is no need for it to be an interface. In this CL, I also took the opportunity to make two small fixes: - remove the 'flexfec_' prefix from some member variables - remove unnecessary use of a stringstream object BUG=webrtc:5654 Review-Url: https://codereview.webrtc.org/2471073003 Cr-Commit-Position: refs/heads/master@{#14919}