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-Commit-Position: refs/heads/master@{#13172}
diff --git a/webrtc/audio/audio_send_stream.cc b/webrtc/audio/audio_send_stream.cc
index 9aa2fc0..d08bfea 100644
--- a/webrtc/audio/audio_send_stream.cc
+++ b/webrtc/audio/audio_send_stream.cc
@@ -127,6 +127,11 @@
          channel_proxy_->SendTelephoneEventOutband(event, duration_ms);
 }
 
+void AudioSendStream::SetMuted(bool muted) {
+  RTC_DCHECK(thread_checker_.CalledOnValidThread());
+  channel_proxy_->SetInputMute(muted);
+}
+
 webrtc::AudioSendStream::Stats AudioSendStream::GetStats() const {
   RTC_DCHECK(thread_checker_.CalledOnValidThread());
   webrtc::AudioSendStream::Stats stats;