Change SetOutputScaling to set a single level, not left/right levels.

talk/media/webrtc/webrtcvoiceengine.h

Index: talk/media/webrtc/webrtcvoiceengine.h
diff --git a/talk/media/webrtc/webrtcvoiceengine.h b/talk/media/webrtc/webrtcvoiceengine.h
index 269920523f4cf93852f12b9119861a3d63f15b94..c9e4a6bca3d0d65012f81884b3a0cfb6ca0fbed0 100644
--- a/talk/media/webrtc/webrtcvoiceengine.h
+++ b/talk/media/webrtc/webrtcvoiceengine.h
@@ -209,7 +209,7 @@ class WebRtcVoiceMediaChannel : public VoiceMediaChannel,
                                     int reporting_threshold,
                                     int penalty_decay,
                                     int type_event_delay) override;
-  bool SetOutputScaling(uint32_t ssrc, double left, double right) override;
+  bool SetOutputScaling(uint32_t ssrc, double volume) override;
 
   bool CanInsertDtmf() override;
   bool InsertDtmf(uint32_t ssrc, int event, int duration, int flags) override;