Implement scoped_const_refptr template.

webrtc/modules/desktop_capture/x11/shared_x_display.h

 /*
  *  Copyright (c) 2013 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 31 matching lines @@
   // Creates a new X11 Display for the |display_name|. NULL is returned if X11
   // connection failed. Equivalent to CreateDefault() when |display_name| is
   // empty.
   static rtc::scoped_refptr<SharedXDisplay> Create(
       const std::string& display_name);
 
   // Creates X11 Display connection for the default display (e.g. specified in
   // DISPLAY). NULL is returned if X11 connection failed.
   static rtc::scoped_refptr<SharedXDisplay> CreateDefault();
 
-  void AddRef() { ++ref_count_; }
-  void Release() {
+  void AddRef() const { ++ref_count_; }
+  void Release() const {
     if (--ref_count_ == 0)
       delete this;
   }
 
   Display* display() { return display_; }
 
   // Adds a new event |handler| for XEvent's of |type|.
   void AddEventHandler(int type, XEventHandler* handler);
 
   // Removes event |handler| added using |AddEventHandler|. Doesn't do anything
   // if |handler| is not registered.
   void RemoveEventHandler(int type, XEventHandler* handler);
 
   // Processes pending XEvents, calling corresponding event handlers.
   void ProcessPendingXEvents();
 
  private:
   typedef std::map<int, std::vector<XEventHandler*> > EventHandlersMap;
 
   ~SharedXDisplay();
 
-  Atomic32 ref_count_;
+  mutable Atomic32 ref_count_;
   Display* display_;
 
   EventHandlersMap event_handlers_;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(SharedXDisplay);
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_DESKTOP_CAPTURE_X11_SHARED_X_DISPLAY_H_