Remove unused output parameter in VCMReceiver::FrameForDecoding().

BUG=
R=pbos@webrtc.org

Review URL: https://codereview.webrtc.org/2104863002 .

Cr-Original-Commit-Position: refs/heads/master@{#13310}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 31b2ec4e0df1bd2ed24bfdd79acde69b9ffc821e
4 files changed