Replace NULL with nullptr in all C++ files.

webrtc/modules/desktop_capture/mouse_cursor_monitor_x11.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 74 matching lines @@
   int xfixes_event_base_;
   int xfixes_error_base_;
 
   std::unique_ptr<MouseCursor> cursor_shape_;
 };
 
 MouseCursorMonitorX11::MouseCursorMonitorX11(
     const DesktopCaptureOptions& options,
     Window window)
     : x_display_(options.x_display()),
-      callback_(NULL),
+      callback_(nullptr),
       mode_(SHAPE_AND_POSITION),
       window_(window),
       have_xfixes_(false),
       xfixes_event_base_(-1),
       xfixes_error_base_(-1) {
   // Set a default initial cursor shape in case XFixes is not present.
   const int kSize = 5;
   std::unique_ptr<DesktopFrame> default_cursor(
       new BasicDesktopFrame(DesktopSize(kSize, kSize)));
   const uint8_t pixels[kSize * kSize] = {
@@ skipping 124 matching lines @@
 
   XFree(img);
 
   cursor_shape_.reset(new MouseCursor(image.release(), hotspot));
 }
 
 // static
 MouseCursorMonitor* MouseCursorMonitor::CreateForWindow(
     const DesktopCaptureOptions& options, WindowId window) {
   if (!options.x_display())
-    return NULL;
+    return nullptr;
   window = GetTopLevelWindow(options.x_display()->display(), window);
   if (window == None)
-    return NULL;
+    return nullptr;
   return new MouseCursorMonitorX11(options, window);
 }
 
 MouseCursorMonitor* MouseCursorMonitor::CreateForScreen(
     const DesktopCaptureOptions& options,
     ScreenId screen) {
   if (!options.x_display())
-    return NULL;
+    return nullptr;
   return new MouseCursorMonitorX11(
       options, DefaultRootWindow(options.x_display()->display()));
 }
 
 }  // namespace webrtc