Add AudioSendStream::SetMuted() method and use it in WVoMC::MuteStream().

Removes the need to use VoEVolume::SetInputMute()/GetInputMute().

BUG=webrtc:4690
NOTRY=true

Review-Url: https://codereview.webrtc.org/2066973002
Cr-Original-Commit-Position: refs/heads/master@{#13172}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 9421853e178151e5bf6f098a739da7a3db39528a
12 files changed