Replace NULL with nullptr in all C++ files.

webrtc/modules/desktop_capture/win/scoped_thread_desktop.cc

Index: webrtc/modules/desktop_capture/win/scoped_thread_desktop.cc
diff --git a/webrtc/modules/desktop_capture/win/scoped_thread_desktop.cc b/webrtc/modules/desktop_capture/win/scoped_thread_desktop.cc
index 2d829d329361b4a45a22353645b4be6ec8c65810..7680459ab47f4c2e104093e9ea2a84108d110926 100644
--- a/webrtc/modules/desktop_capture/win/scoped_thread_desktop.cc
+++ b/webrtc/modules/desktop_capture/win/scoped_thread_desktop.cc
@@ -25,7 +25,7 @@ ScopedThreadDesktop::~ScopedThreadDesktop() {
 }
 
 bool ScopedThreadDesktop::IsSame(const Desktop& desktop) {
-  if (assigned_.get() != NULL) {
+  if (assigned_.get() != nullptr) {
     return assigned_->IsSame(desktop);
   } else {
     return initial_->IsSame(desktop);
@@ -33,7 +33,7 @@ bool ScopedThreadDesktop::IsSame(const Desktop& desktop) {
 }
 
 void ScopedThreadDesktop::Revert() {
-  if (assigned_.get() != NULL) {
+  if (assigned_.get() != nullptr) {
     initial_->SetThreadDesktop();
     assigned_.reset();
   }