Replace NULL with nullptr in all C++ files.

webrtc/modules/desktop_capture/win/screen_capture_utils.cc

Index: webrtc/modules/desktop_capture/win/screen_capture_utils.cc
diff --git a/webrtc/modules/desktop_capture/win/screen_capture_utils.cc b/webrtc/modules/desktop_capture/win/screen_capture_utils.cc
index 7d9203f27b6915e72a5415c27f79988e67e10ae8..a267ab514ef00d656c9a03108346de53686796fe 100644
--- a/webrtc/modules/desktop_capture/win/screen_capture_utils.cc
+++ b/webrtc/modules/desktop_capture/win/screen_capture_utils.cc
@@ -23,7 +23,7 @@ bool GetScreenList(DesktopCapturer::SourceList* screens) {
   for (int device_index = 0;; ++device_index) {
     DISPLAY_DEVICE device;
     device.cb = sizeof(device);
-    enum_result = EnumDisplayDevices(NULL, device_index, &device, 0);
+    enum_result = EnumDisplayDevices(nullptr, device_index, &device, 0);
 
     // |enum_result| is 0 if we have enumerated all devices.
     if (!enum_result)
@@ -46,7 +46,7 @@ bool IsScreenValid(DesktopCapturer::SourceId screen, std::wstring* device_key) {
 
   DISPLAY_DEVICE device;
   device.cb = sizeof(device);
-  BOOL enum_result = EnumDisplayDevices(NULL, screen, &device, 0);
+  BOOL enum_result = EnumDisplayDevices(nullptr, screen, &device, 0);
   if (enum_result)
     *device_key = device.DeviceKey;
 
@@ -64,7 +64,7 @@ DesktopRect GetScreenRect(DesktopCapturer::SourceId screen,
 
   DISPLAY_DEVICE device;
   device.cb = sizeof(device);
-  BOOL result = EnumDisplayDevices(NULL, screen, &device, 0);
+  BOOL result = EnumDisplayDevices(nullptr, screen, &device, 0);
   if (!result)
     return DesktopRect();