141     string error_message;  in Init()  local
144                           &error_message)) {  in Init()
145       LOG(ERROR) << "Setting the channel failed: " << error_message;  in Init()
166                                           string* error_message) {  in SetTargetChannel()  argument
174   if (!IsValidChannel(new_target_channel, error_message)) {  in SetTargetChannel()
183     if (error_message)  in SetTargetChannel()
184       *error_message = "Error storing the new channel value.";  in SetTargetChannel()
207                                         string* error_message) const {  in IsValidChannel()
210       if (error_message) {  in IsValidChannel()
211         *error_message = base::StringPrintf(  in IsValidChannel()
222     if (error_message) {  in IsValidChannel()
223       *error_message =  in IsValidChannel()