Add mistakenly removed VAD enabling function.

This resolves the unknown VAD status warnings introduced in r845.

BUG=
TEST=voe_cmd_test

Review URL: http://webrtc-codereview.appspot.com/252004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@879 4adac7df-926f-26a2-2b94-8c16560cd09d

src/voice_engine/main/source/channel.cc

@@ -1401,6 +1401,8 @@ Channel::Init()
         // out-of-band Dtmf tones are played out by default
         (_audioCodingModule.SetDtmfPlayoutStatus(true) == -1) ||
 #endif
+        // Enable RX VAD by default (improves output mixing).
+        (_audioCodingModule.SetReceiveVADStatus(true) == -1) ||
         (_audioCodingModule.InitializeSender() == -1))
     {
         _engineStatisticsPtr->SetLastError(