Remove unused render callback method+pointer in IncomingVideoStream.

Review-Url: https://codereview.webrtc.org/2032003002
Cr-Original-Commit-Position: refs/heads/master@{#13009}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 5724b7317ee9ceaae2b131fda645c72ed29e282d
2 files changed