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

talk/session/media/channel.cc

Index: talk/session/media/channel.cc
diff --git a/talk/session/media/channel.cc b/talk/session/media/channel.cc
index 57d09a2d6fda80311addd7f0c26bee76223c55a9..c7d83cedaf1b12dda801b25d9037cad343e63dfb 100644
--- a/talk/session/media/channel.cc
+++ b/talk/session/media/channel.cc
@@ -1347,9 +1347,9 @@ bool VoiceChannel::InsertDtmf(uint32_t ssrc,
                              ssrc, event_code, duration, flags));
 }
 
-bool VoiceChannel::SetOutputScaling(uint32_t ssrc, double left, double right) {
+bool VoiceChannel::SetOutputScaling(uint32_t ssrc, double volume) {
   return InvokeOnWorker(Bind(&VoiceMediaChannel::SetOutputScaling,
-                             media_channel(), ssrc, left, right));
+                             media_channel(), ssrc, volume));
 }
 
 bool VoiceChannel::GetStats(VoiceMediaInfo* stats) {