Get the name and message from DOMException correctly

tools/dom/templates/html/impl/impl_DOMException.darttemplate

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of $LIBRARYNAME;
 
 $(ANNOTATIONS)$(NATIVESPEC)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS {
 
   static const String INDEX_SIZE = 'IndexSizeError';
   static const String HIERARCHY_REQUEST = 'HierarchyRequestError';
@@ skipping 31 matching lines @@
     return errorName;
   }
 $endif
 $if JSINTEROP
   String _name;
   String _message;
 
   // To suppress missing implicit constructor warnings.
   factory DomException._() { throw new UnsupportedError("Not supported"); }
 
   @Deprecated("Internal Use Only")

[Jacob, 2017/06/08 23:50:00]

probably dead but do a text search of
third_party/webkit 
internalCreateDomException

to make sure we aren't calling this directly from C++

-  static DomException internalCreateDomException() {
-    return new DomException._internalWrap();
-  }
-
-  external factory DomException._internalWrap();
-
-  @Deprecated("Internal Use Only")
   DomException.internal_() { }
 
   @Deprecated("Internal Use Only")
   DomException.jsInterop(String m) {
     var name_index = m.indexOf(': ');
     if (name_index < 0) {
       _name = "";
       _message = m;
     } else {
       _name = m.substring(0, name_index);
       _message = m.substring(name_index + 1).trim();
     }
   }
 
   @DomName('DOMException.message')
   @DocsEditable()
-  String get message => _message;
+  String get message => _message ??
+     (_message = _blink.BlinkDOMException.instance.message_Getter_(this));
 
   @DomName('DOMException.name')
   @DocsEditable()
-  String get name => _name;
+  String get name => _name ??
+      (_name = _blink.BlinkDOMException.instance.name_Getter_(this));
 
   @DomName('DOMException.toString')
   @DocsEditable()
-  String toString() => "${_name}: $_message";
+  String toString() => "$name: $message";
 
 $else
 $!MEMBERS
 $endif
 $if DART2JS
   @DomName('DOMException.toString')
   @DocsEditable()
   String toString() => JS('String', 'String(#)', this);
 $endif
 }