Remove usage of VoEBase::AssociateSendChannel() from WVoMC.

- Functionality now implemented in AudioReceiveStream and Call.
- Added some missing function to MockChannelProxy.

BUG=webrtc:4690

Review-Url: https://codereview.webrtc.org/2461523002
Cr-Original-Commit-Position: refs/heads/master@{#15072}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 7602aabdc0414f30756b2414e8623e41478a7503
14 files changed