Remove mutable from rtc::CriticalSections.

webrtc/voice_engine/statistics.h

 /*
  *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 21 matching lines @@
     int32_t SetUnInitialized();
     bool Initialized() const;
     int32_t SetLastError(int32_t error) const;
     int32_t SetLastError(int32_t error, TraceLevel level) const;
     int32_t SetLastError(int32_t error,
                          TraceLevel level,
                          const char* msg) const;
     int32_t LastError() const;
 
  private:
-    mutable rtc::CriticalSection lock_;
+    rtc::CriticalSection lock_;
     const uint32_t _instanceId;
     mutable int32_t _lastError;
     bool _isInitialized;
 };
 
 }  // namespace voe
 
 }  // namespace webrtc
 
 #endif // WEBRTC_VOICE_ENGINE_STATISTICS_H