fix to run against latest analyzer

lib/src/dart_sdk.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.
 
 /// Common logic needed to provide a Dart SDK to the analyzer's resolver. This
 /// includes logic to determine where the sdk is located in the filesystem, and
 /// definitions to provide mock sdks.
 
 import 'package:analyzer/src/generated/engine.dart'
     show AnalysisContext, TimestampedData;
 import 'package:analyzer/src/generated/sdk.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/context/context.dart';
 
 /// Dart SDK which contains a mock implementation of the SDK libraries. May be
 /// used to speed up execution when most of the core libraries is not needed.
 class MockDartSdk implements DartSdk {
   final Map<Uri, _MockSdkSource> _sources = {};
   final bool reportMissing;
   final Map<String, SdkLibrary> _libs = {};
   final String sdkVersion = '0';
   List<String> get uris => _sources.keys.map((uri) => '$uri').toList();
-  final AnalysisContext context = new SdkAnalysisContext();
+  final AnalysisContext context = new SdkAnalysisContext(null);
   DartUriResolver _resolver;
   DartUriResolver get resolver => _resolver;
 
   MockDartSdk(Map<String, String> sources, {this.reportMissing}) {
     sources.forEach((uriString, contents) {
       var uri = Uri.parse(uriString);
       _sources[uri] = new _MockSdkSource(uri, contents);
       _libs[uriString] = new SdkLibraryImpl(uri.path)
         ..setDart2JsLibrary()
         ..setVmLibrary();
@@ skipping 139 matching lines @@
         ''',
   'dart:math': '''
         library dart.math;
         class Random {
           bool nextBool() {}
         }
         num min(num x, num y) {}
         num max(num x, num y) {}
         ''',
 };