Replace NULL with nullptr in all C++ files.

webrtc/modules/desktop_capture/mac/window_list_utils.cc

Index: webrtc/modules/desktop_capture/mac/window_list_utils.cc
diff --git a/webrtc/modules/desktop_capture/mac/window_list_utils.cc b/webrtc/modules/desktop_capture/mac/window_list_utils.cc
index bcb8798c39d9e9d9dbf90527a8e74752cd47a6d7..c9160d80ac4d7627bc1675b7b2e6dffd0a5dac93 100644
--- a/webrtc/modules/desktop_capture/mac/window_list_utils.cc
+++ b/webrtc/modules/desktop_capture/mac/window_list_utils.cc
@@ -103,7 +103,7 @@ bool IsWindowFullScreen(
 // Returns true if the window is minimized.
 bool IsWindowMinimized(CGWindowID id) {
   CFArrayRef window_id_array =
-      CFArrayCreate(NULL, reinterpret_cast<const void **>(&id), 1, NULL);
+      CFArrayCreate(nullptr, reinterpret_cast<const void**>(&id), 1, nullptr);
   CFArrayRef window_array =
       CGWindowListCreateDescriptionFromArray(window_id_array);
   bool minimized = false;