Run clang-modernize -use-nullptr over src/extensions/.

extensions/shell/browser/desktop_controller.cc

Index: extensions/shell/browser/desktop_controller.cc
diff --git a/extensions/shell/browser/desktop_controller.cc b/extensions/shell/browser/desktop_controller.cc
index 7bf6bc52c0832b550ff41528189acd683d376606..ea39712bb040c3ff5fd5114b69139ab4a96356ec 100644
--- a/extensions/shell/browser/desktop_controller.cc
+++ b/extensions/shell/browser/desktop_controller.cc
@@ -10,7 +10,7 @@
 namespace extensions {
 namespace {
 
-DesktopController* g_instance = NULL;
+DesktopController* g_instance = nullptr;
 
 }  // namespace
 
@@ -26,7 +26,7 @@ DesktopController::DesktopController() {
 
 DesktopController::~DesktopController() {
   DCHECK(g_instance);
-  g_instance = NULL;
+  g_instance = nullptr;
 }
 
 }  // namespace extensions