Test ImportElement and fix PrefixElementZ.isTopLevel

tests/compiler/dart2js/serialization/equivalence_test.dart

 // Copyright (c) 2015, 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 dart2js.serialization_test;
 
 import 'dart:io';
 import '../memory_compiler.dart';
 import 'package:async_helper/async_helper.dart';
 import 'package:compiler/src/commandline_options.dart';
@@ skipping 335 matching lines @@
     check(element1, element2, 'libraryName',
           element1.libraryName, element2.libraryName);
     visitMembers(element1, element2);
     visit(element1.entryCompilationUnit, element2.entryCompilationUnit);
 
     checkElementLists(
         element1, element2, 'compilationUnits',
         LibrarySerializer.getCompilationUnits(element1),
         LibrarySerializer.getCompilationUnits(element2));
 
-    checkElementListIdentities(
+    checkElementLists(
         element1, element2, 'imports',
         LibrarySerializer.getImports(element1),
         LibrarySerializer.getImports(element2));
-    checkElementListIdentities(
+    checkElementLists(
         element1, element2, 'exports', element1.exports, element2.exports);
 
     checkElementListIdentities(
         element1, element2, 'importScope',
         LibrarySerializer.getImportedElements(element1),
         LibrarySerializer.getImportedElements(element2));
 
     checkElementListIdentities(
         element1, element2, 'exportScope',
         LibrarySerializer.getExportedElements(element1),
@@ skipping 482 matching lines @@
     // TODO(johnniwinther): Check members.
   }
 
   @override
   void visitErroneousElement(
       ErroneousElement element1, ErroneousElement element2) {
     check(element1, element2, 'messageKind',
         element1.messageKind, element2.messageKind);
   }
 }