Replace NULL with nullptr in all C++ files.

webrtc/modules/desktop_capture/x11/x_error_trap.cc

 /*
  *  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 19 matching lines @@
   assert(g_xserver_error_trap_enabled);
   g_last_xserver_error_code = error_event->error_code;
   return 0;
 }
 
 #endif  // !defined(TOOLKIT_GTK)
 
 }  // namespace
 
 XErrorTrap::XErrorTrap(Display* display)
-    : original_error_handler_(NULL),
-      enabled_(true) {
+    : original_error_handler_(nullptr), enabled_(true) {
 #if defined(TOOLKIT_GTK)
   gdk_error_trap_push();
 #else  // !defined(TOOLKIT_GTK)
   assert(!g_xserver_error_trap_enabled);
   original_error_handler_ = XSetErrorHandler(&XServerErrorHandler);
   g_xserver_error_trap_enabled = true;
   g_last_xserver_error_code = 0;
 #endif  // !defined(TOOLKIT_GTK)
 }
 
 int XErrorTrap::GetLastErrorAndDisable() {
   enabled_ = false;
 #if defined(TOOLKIT_GTK)
   return gdk_error_trap_push();
 #else  // !defined(TOOLKIT_GTK)
   assert(g_xserver_error_trap_enabled);
   XSetErrorHandler(original_error_handler_);
   g_xserver_error_trap_enabled = false;
   return g_last_xserver_error_code;
 #endif  // !defined(TOOLKIT_GTK)
 }
 
 XErrorTrap::~XErrorTrap() {
   if (enabled_)
     GetLastErrorAndDisable();
 }
 
 }  // namespace webrtc