Fix issues from CL 3009573002.

pkg/front_end/lib/src/fasta/kernel/kernel_target.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.kernel_target;
 
 import 'dart:async' show Future;
 
 import 'package:kernel/ast.dart'
     show
@@ skipping 353 matching lines @@
     uriToSource.addAll(dillTarget.loader.uriToSource);
 
     // TODO(ahe): Remove this line. Kernel seems to generate a default line map
     // that used when there's no fileUri on an element. Instead, ensure all
     // elements have a fileUri.
     uriToSource[""] = new Source(<int>[0], const <int>[]);
     Program program = new Program(
         nameRoot: nameRoot, libraries: libraries, uriToSource: uriToSource);
     if (loader.first != null) {
       // TODO(sigmund): do only for full program
-      Builder builder = loader.first.lookup("main", -1, null);
+      Builder builder = loader.first.exportScope.lookup("main", -1, null);
       if (builder is KernelProcedureBuilder) {
         program.mainMethod = builder.procedure;
       }
     }
 
     ticker.logMs("Linked program");
     return program;
   }
 
   void installDefaultSupertypes() {
@@ skipping 286 matching lines @@
   }
   for (Constructor constructor in superclass.constructors) {
     if (constructor.name.name.isEmpty) {
       return constructor.function.requiredParameterCount == 0
           ? constructor
           : null;
     }
   }
   return null;
 }