Fix off-by-one in ALSA control name determination.

media/audio/alsa/alsa_util.cc

Index: media/audio/alsa/alsa_util.cc
diff --git a/media/audio/alsa/alsa_util.cc b/media/audio/alsa/alsa_util.cc
index 76bdfbf9410480d4c6dfda89caafbb9539b7e1bf..b94cd17bf05e8ef8ace243ea7aeb5360b1d38395 100644
--- a/media/audio/alsa/alsa_util.cc
+++ b/media/audio/alsa/alsa_util.cc
@@ -54,9 +54,9 @@ static std::string DeviceNameToControlName(const std::string& device_name) {
     // deviceName: "front:CARD=Intel,DEV=0", controlName: "hw:CARD=Intel".
     // deviceName: "default:CARD=Intel", controlName: "CARD=Intel".
     size_t pos2 = device_name.find(',');
-    control_name = (pos2 == std::string::npos) ?
-        device_name.substr(pos1) :
-        kMixerPrefix + device_name.substr(pos1, pos2 - pos1);
+    control_name = (pos2 == std::string::npos)
+                       ? device_name.substr(pos1 + 1)
+                       : kMixerPrefix + device_name.substr(pos1, pos2 - pos1);
   }
 
   return control_name;