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

webrtc/media/engine/fakewebrtccall.cc

Index: webrtc/media/engine/fakewebrtccall.cc
diff --git a/webrtc/media/engine/fakewebrtccall.cc b/webrtc/media/engine/fakewebrtccall.cc
index 41b34750e71e873f434d2be068dc262c7f89a3e3..b1ba47828f137b98060825a0c7a626679e3e93dd 100644
--- a/webrtc/media/engine/fakewebrtccall.cc
+++ b/webrtc/media/engine/fakewebrtccall.cc
@@ -47,6 +47,10 @@ bool FakeAudioSendStream::SendTelephoneEvent(int payload_type, int event,
   return true;
 }
 
+void FakeAudioSendStream::SetMuted(bool muted) {
+  muted_ = muted;
+}
+
 webrtc::AudioSendStream::Stats FakeAudioSendStream::GetStats() const {
   return stats_;
 }