Add int.toString() to analyzer mock SDK.

pkg/analyzer/test/src/context/mock_sdk.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 analyzer.test.src.context.mock_sdk;
 
 import 'package:analyzer/file_system/file_system.dart' as resource;
 import 'package:analyzer/file_system/memory_file_system.dart' as resource;
 import 'package:analyzer/src/context/cache.dart';
 import 'package:analyzer/src/context/context.dart';
@@ skipping 191 matching lines @@
   int operator ^(int other);
   int operator ~();
   int operator <<(int shiftAmount);
   int operator >>(int shiftAmount);
 
   int operator -();
 
   external static int parse(String source,
                             { int radix,
                               int onError(String source) });
+
+  String toString();
 }
 
 abstract class double extends num {
   static const double NAN = 0.0 / 0.0;
   static const double INFINITY = 1.0 / 0.0;
   static const double NEGATIVE_INFINITY = -INFINITY;
   static const double MIN_POSITIVE = 5e-324;
   static const double MAX_FINITE = 1.7976931348623157e+308;
 
   double remainder(num other);
@@ skipping 407 matching lines @@
 
   @override
   AnalysisCache createCacheFromSourceFactory(SourceFactory factory) {
     if (factory == null) {
       return super.createCacheFromSourceFactory(factory);
     }
     return new AnalysisCache(
         <CachePartition>[AnalysisEngine.instance.partitionManager.forSdk(sdk)]);
   }
 }