Remove mutable from rtc::CriticalSection members.

webrtc/base/messagequeue.h

 /*
  *  Copyright 2004 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 233 matching lines @@
   // The SocketServer is not owned by MessageQueue.
   SocketServer* ss_;
   // If a server isn't supplied in the constructor, use this one.
   scoped_ptr<SocketServer> default_ss_;
   bool fStop_;
   bool fPeekKeep_;
   Message msgPeek_;
   MessageList msgq_;
   PriorityQueue dmsgq_;
   uint32_t dmsgq_next_num_;
-  mutable CriticalSection crit_;
+  CriticalSection crit_;
 
  private:
   RTC_DISALLOW_COPY_AND_ASSIGN(MessageQueue);
 };
 
 }  // namespace rtc
 
 #endif  // WEBRTC_BASE_MESSAGEQUEUE_H_