Replace NULL with nullptr in all C++ files.

webrtc/modules/desktop_capture/win/screen_capturer_win_magnifier.cc

Index: webrtc/modules/desktop_capture/win/screen_capturer_win_magnifier.cc
diff --git a/webrtc/modules/desktop_capture/win/screen_capturer_win_magnifier.cc b/webrtc/modules/desktop_capture/win/screen_capturer_win_magnifier.cc
index 96348ca49455bc5f1b0d1ab4b7bf75488f0bffce..f29e6d09dbf7b31cffe70df5db7b4f8e6dc5c9fb 100644
--- a/webrtc/modules/desktop_capture/win/screen_capturer_win_magnifier.cc
+++ b/webrtc/modules/desktop_capture/win/screen_capturer_win_magnifier.cc
@@ -52,7 +52,7 @@ ScreenCapturerWinMagnifier::~ScreenCapturerWinMagnifier() {
     FreeLibrary(mag_lib_handle_);
 
   if (desktop_dc_)
-    ReleaseDC(NULL, desktop_dc_);
+    ReleaseDC(nullptr, desktop_dc_);
 }
 
 void ScreenCapturerWinMagnifier::Start(Callback* callback) {
@@ -91,11 +91,11 @@ void ScreenCapturerWinMagnifier::CaptureFrame() {
   // Switch to the desktop receiving user input if different from the current
   // one.
   std::unique_ptr<Desktop> input_desktop(Desktop::GetInputDesktop());
-  if (input_desktop.get() != NULL && !desktop_.IsSame(*input_desktop)) {
+  if (input_desktop.get() != nullptr && !desktop_.IsSame(*input_desktop)) {
     // Release GDI resources otherwise SetThreadDesktop will fail.
     if (desktop_dc_) {
-      ReleaseDC(NULL, desktop_dc_);
-      desktop_dc_ = NULL;
+      ReleaseDC(nullptr, desktop_dc_);
+      desktop_dc_ = nullptr;
     }
     // If SetThreadDesktop() fails, the thread is still assigned a desktop.
     // So we can continue capture screen bits, just from the wrong desktop.
@@ -157,8 +157,8 @@ bool ScreenCapturerWinMagnifier::CaptureImage(const DesktopRect& rect) {
 
   // Set the magnifier control to cover the captured rect. The content of the
   // magnifier control will be the captured image.
-  BOOL result = SetWindowPos(magnifier_window_, NULL, rect.left(), rect.top(),
-                             rect.width(), rect.height(), 0);
+  BOOL result = SetWindowPos(magnifier_window_, nullptr, rect.left(),
+                             rect.top(), rect.width(), rect.height(), 0);
   if (!result) {
     LOG_F(LS_WARNING) << "Failed to call SetWindowPos: " << GetLastError()
                       << ". Rect = {" << rect.left() << ", " << rect.top()