Low risk non-nullable => nullable change

third_party/WebKit/Source/modules/webmidi/MIDIPort.idl

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 40 matching lines @@
 };
 
 // https://webaudio.github.io/web-midi-api/#MIDIPort
 
 [
     ActiveScriptWrappable,
     DependentLifetime,
 ] interface MIDIPort : EventTarget {
     readonly attribute MIDIPortConnectionState connection;
     readonly attribute DOMString id;
-    readonly attribute DOMString manufacturer;
-    readonly attribute DOMString name;
+    readonly attribute DOMString? manufacturer;

[foolip, 2016/12/13 22:37:31]

Oh my, I've lied again. This would change the generated code I think, to make
the return value change from "" to null if a null WTF::String is returned.

Maybe it's best to compare the generated code to make sure what will remain
really doesn't change anything.

+    readonly attribute DOMString? name;
     readonly attribute MIDIPortDeviceState state;
     readonly attribute MIDIPortType type;
-    readonly attribute DOMString version;
+    readonly attribute DOMString? version;
 
     attribute EventHandler onstatechange;
 
     [CallWith=ScriptState] Promise open();
     [CallWith=ScriptState] Promise close();
 };