Remove mutable from rtc::CriticalSection members.

webrtc/modules/audio_coding/test/Channel.h

Index: webrtc/modules/audio_coding/test/Channel.h
diff --git a/webrtc/modules/audio_coding/test/Channel.h b/webrtc/modules/audio_coding/test/Channel.h
index 3dcd499c03cdc6bfe5cf5bb1cf27239bdc10f38c..5910fade25cba02990e2787073df4066a45fdce3 100644
--- a/webrtc/modules/audio_coding/test/Channel.h
+++ b/webrtc/modules/audio_coding/test/Channel.h
@@ -100,7 +100,7 @@ class Channel : public AudioPacketizationCallback {
   // 60msec * 32 sample(max)/msec * 2 description (maybe) * 2 bytes/sample
   uint8_t _payloadData[60 * 32 * 2 * 2];
 
-  mutable rtc::CriticalSection _channelCritSect;
+  rtc::CriticalSection _channelCritSect;
   FILE* _bitStreamFile;
   bool _saveBitStream;
   int16_t _lastPayloadType;