Check the number of playout channels instead of the send channels in StopPlayout()

BUG=2467
R=henrika@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/2420004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@4989 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/voice_engine/shared_data.h b/voice_engine/shared_data.h
index 7c7ad5c..dd76e96 100644
--- a/voice_engine/shared_data.h
+++ b/voice_engine/shared_data.h
@@ -56,7 +56,8 @@
       _audioDeviceLayer = layer;
     }
 
-    uint16_t NumOfSendingChannels();
+    int NumOfSendingChannels();
+    int NumOfPlayingChannels();
 
     // Convenience methods for calling statistics().SetLastError().
     void SetLastError(int32_t error) const;