Do not allow native syntax on all libraries.

dart/frog/leg/scanner/class_element_parser.dart

 // Copyright (c) 2011, 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.
 
 class ClassElementParser extends PartialParser {
   ClassElementParser(Listener listener) : super(listener);
 
   Token parseClassBody(Token token) => fullParseClassBody(token);
 }
 
@@ skipping 21 matching lines @@
 
   Token position() => beginToken;
 
   bool isInterface() => beginToken.stringValue === "interface";
 }
 
 class MemberListener extends NodeListener {
   final ClassElement enclosingElement;
 
   MemberListener(DiagnosticListener listener,
-                 [Element this.enclosingElement = null])
-    : super(listener);
+                 Element enclosingElement)
+    : this.enclosingElement = enclosingElement,
+      super(listener, enclosingElement.getCompilationUnit());
 
   bool isConstructorName(Node nameNode) {
     if (enclosingElement === null ||
         enclosingElement.kind != ElementKind.CLASS) {
       return false;
     }
     SourceString name;
     if (nameNode.asIdentifier() !== null) {
       name = nameNode.asIdentifier().source;
     } else {
@@ skipping 69 matching lines @@
   void endInitializer(Token assignmentOperator) {
     pushNode(null); // Super expects an expression, but
                     // ClassElementParser just skips expressions.
     super.endInitializer(assignmentOperator);
   }
 
   void endInitializers(int count, Token beginToken, Token endToken) {
     pushNode(null);
   }
 }