Change destruction order to fix potential invalid pointer dereference.

webrtc/modules/desktop_capture/screen_capturer_mac.mm

 /*
  *  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 372 matching lines @@
 };
 
 ScreenCapturerMac::ScreenCapturerMac(
     rtc::scoped_refptr<DesktopConfigurationMonitor> desktop_config_monitor)
     : desktop_config_monitor_(desktop_config_monitor) {
   display_stream_manager_ = new DisplayStreamManager;
 }
 
 ScreenCapturerMac::~ScreenCapturerMac() {
   ReleaseBuffers();
+  UnregisterRefreshAndMoveHandlers();
   display_stream_manager_->PrepareForSelfDestruction();
-  UnregisterRefreshAndMoveHandlers();
   dlclose(app_services_library_);
   dlclose(opengl_library_);
 }
 
 bool ScreenCapturerMac::Init() {
   desktop_config_monitor_->Lock();
   desktop_config_ = desktop_config_monitor_->desktop_configuration();
   desktop_config_monitor_->Unlock();
   if (!RegisterRefreshAndMoveHandlers()) {
     return false;
@@ skipping 626 matching lines @@
   }
 
   if (options.detect_updated_region()) {
     capturer.reset(new ScreenCapturerDifferWrapper(std::move(capturer)));
   }
 
   return capturer.release();
 }
 
 }  // namespace webrtc