Get back recording 'implements' and 'extends' keyword on NodeList

lib/compiler/implementation/dart_backend/emitter.dart

 // Copyright (c) 2012, 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.
 
 /**
  * Dart backend helper for converting program IR back to source code.
  */
 class Emitter {
 
   final Compiler compiler;
@@ skipping 25 matching lines @@
       sb.add(unparser.unparse(classNode.typeParameters));
     }
     renamer.setContext(classElement);
     if (classNode.extendsKeyword !== null) {
       sb.add(' ');
       classNode.extendsKeyword.value.printOn(sb);
       sb.add(' ');
       sb.add(unparser.unparse(classNode.superclass));
     }
     if (!classNode.interfaces.isEmpty()) {
-      sb.add(classElement.isInterface() ? ' extends ' : ' implements ');
+      sb.add(' ');
       sb.add(unparser.unparse(classNode.interfaces));
     }
     if (classNode.defaultClause !== null) {
       sb.add(' default ');
       sb.add(unparser.unparse(classNode.defaultClause));
     }
     sb.add('{');
     innerElements.forEach((element) {
       // TODO(smok): Filter out default constructors here.
       outputElement(element);
@@ skipping 33 matching lines @@
       if (!uri.startsWith('dart:')) continue;
       final lib = libraries[uri];
       if (renamer.imports.containsKey(lib)) {
         result.add('#import("$uri", prefix: "${renamer.imports[lib]}");');
       }
     }
     result.add(sb);
     return result.toString();
   }
 }