kernel->ssa: get simple constructors working

tests/compiler/dart2js/kernel/simple_function_test.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.
 
 import 'package:test/test.dart';
 
 import 'helper.dart' show check;
 
 main() {
   group('compile function that returns a value', () {
@@ skipping 24 matching lines @@
 
   test('compile function that returns its argument', () {
     String code = '''
       foo(x) {
         return x;
       }
 
       main() {
         foo(1);
       }''';
-    return check(code, entry: 'foo');
+    return check(code, lookup: 'foo');
   });
 }