cache pub list results

pkg/analyzer/test/source/package_map_provider_test.dart

 // Copyright (c) 2014, 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 test.package.map.provider;
 
-import 'dart:convert';
-
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:analyzer/source/package_map_provider.dart';
 import 'package:analyzer/source/pub_package_map_provider.dart';
 import 'package:analyzer/src/generated/sdk_io.dart';
 import 'package:unittest/unittest.dart';
 
 main() {
   groupSep = ' | ';
 
   group('PubPackageMapProvider', () {
     group('parsePackageMap', () {
       MemoryResourceProvider resourceProvider;
       PubPackageMapProvider packageMapProvider;
       const String projectPath = '/path/to/project';
       Folder projectFolder;
 
       setUp(() {
         resourceProvider = new MemoryResourceProvider();
         packageMapProvider =
             new PubPackageMapProvider(resourceProvider, DirectoryBasedDartSdk.defaultSdk);
         projectFolder = resourceProvider.newFolder(projectPath);
       });
 
       PackageMapInfo parsePackageMap(Object obj) {
-        return packageMapProvider.parsePackageMap(
-            JSON.encode(obj),
-            projectFolder);
+        return packageMapProvider.parsePackageMap(obj, projectFolder);
       }
 
       test('normal folder', () {
         String packageName = 'foo';
         String folderPath = '/path/to/folder';
         resourceProvider.newFolder(folderPath);
         Map<String, List<Folder>> result = parsePackageMap({
           'packages': {
             packageName: folderPath
           }
@@ skipping 72 matching lines @@
         Set<String> dependencies = parsePackageMap({
           'packages': {},
           'input_files': [relativeDependencyPath]
         }).dependencies;
         expect(dependencies, hasLength(1));
         expect(dependencies, contains(dependencyPath));
       });
     });
   });
 }