Mojo: NULL -> nullptr in mojo/public/cpp/bindings and also for the bindings generator.

mojo/public/cpp/bindings/lib/string_serialization.cc

Index: mojo/public/cpp/bindings/lib/string_serialization.cc
diff --git a/mojo/public/cpp/bindings/lib/string_serialization.cc b/mojo/public/cpp/bindings/lib/string_serialization.cc
index 10d09e23a91796029782dd15bf40823b8fd638c2..a0544c07273ed228d73bda55720a9a7a59b99ef6 100644
--- a/mojo/public/cpp/bindings/lib/string_serialization.cc
+++ b/mojo/public/cpp/bindings/lib/string_serialization.cc
@@ -23,7 +23,7 @@ void Serialize_(const String& input, internal::Buffer* buf,
       memcpy(result->storage(), input.data(), input.size());
     *output = result;
   } else {
-    *output = NULL;
+    *output = nullptr;
   }
 }