Used by callMethod to get the JS object for each argument passed if the argument is a Dart class instance that delegates to a DOM object. See wrap_jso defined in dart:html.
Source
unwrap_jso(dartClass_instance) {
try {
if (dartClass_instance != null)
return dartClass_instance is NativeFieldWrapperClass2 ?
dartClass_instance.blink_jsObject : dartClass_instance;
else
return null;
} catch(NoSuchMethodException) {
// No blink_jsObject then return the dartClass_instance is probably an
// array that was already converted to a Dart class e.g., Uint8ClampedList.
return dartClass_instance;
}
}