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

extensions/renderer/messaging_bindings.cc

Index: extensions/renderer/messaging_bindings.cc
diff --git a/extensions/renderer/messaging_bindings.cc b/extensions/renderer/messaging_bindings.cc
index 860a99e994ab4bcfecc288c9f930cb71503db97e..3d83e00579b5891c1b91ffe387a27ed2a153670e 100644
--- a/extensions/renderer/messaging_bindings.cc
+++ b/extensions/renderer/messaging_bindings.cc
@@ -216,7 +216,7 @@ class ExtensionImpl : public ObjectBackedNativeHandler {
         return;
       v8::Context::Scope context_scope(context);
       blink::WebScopedMicrotaskSuppression suppression;
-      callback->Call(context->Global(), 0, NULL);
+      callback->Call(context->Global(), 0, nullptr);
     }
 
     ScopedPersistent<v8::Object> object_;