[kernel] Fix front_end after previous commit

pkg/kernel/lib/binary/limited_ast_to_binary.dart

 // Copyright (c) 2017, 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.
 
 import 'package:kernel/ast.dart';
 import 'package:kernel/binary/ast_to_binary.dart';
 
 /// Writes libraries that satisfy the [predicate].
 ///
 /// Only the referenced subset of canonical names is indexed and written,
@@ skipping 44 matching lines @@
   void writeLibraries(Program program) {
     var librariesToWrite = program.libraries.where(predicate).toList();
     writeList(librariesToWrite, writeNode);
   }
 
   @override
   void writeNode(Node node) {
     if (node is Library && !predicate(node)) return;
     node.accept(this);
   }
+
+  @override
+  void writeProgramIndex(Program program, List<Library> libraries) {
+    var librariesToWrite = libraries.where(predicate).toList();
+    super.writeProgramIndex(program, librariesToWrite);
+  }
 }
 
 /// Extension of [StringIndexer] that also indexes canonical names of
 /// referenced classes and members.
 class ReferencesStringIndexer extends StringIndexer {
   final List<CanonicalName> referencedNames = <CanonicalName>[];
 
   @override
   defaultMemberReference(Member node) {
     _handleReferencedName(node.canonicalName);
@@ skipping 41 matching lines @@
   }
 
   void _handleReferencedName(CanonicalName name) {
     if (name == null || name.parent == null) return;
     _handleReferencedName(name.parent);
     referencedNames.add(name);
     name.index = -1;
     put(name.name);
   }
 }