Change signature of resolveConstructors.

pkg/front_end/lib/src/fasta/builder/class_builder.dart

 // Copyright (c) 2016, 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.
 
 library fasta.class_builder;
 
 import '../errors.dart' show internalError;
 
 import 'builder.dart'
     show
@@ skipping 42 matching lines @@
 
   Map<String, Builder> get constructors;
 
   Map<String, Builder> get membersInScope => members;
 
   LibraryBuilder get library {
     LibraryBuilder library = parent;
     return library.partOfLibrary ?? library;
   }
 
+  @override
   int resolveConstructors(LibraryBuilder library) {
     if (constructorReferences == null) return 0;
     Scope scope = computeInstanceScope(library.scope);
     for (ConstructorReferenceBuilder ref in constructorReferences) {
       ref.resolveIn(scope);
     }
     return constructorReferences.length;
   }
 
   Scope computeInstanceScope(Scope parent) {
@@ skipping 134 matching lines @@
   }
 
   void addWarning(int charOffset, String message) {
     library.addWarning(charOffset, message, fileUri: fileUri);
   }
 
   void addNit(int charOffset, String message) {
     library.addNit(charOffset, message, fileUri: fileUri);
   }
 }