Begin implementing subtype matching for type inference.

pkg/kernel/lib/testing/mock_sdk_program.dart

 // Copyright (c) 2017, 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.
 
 import 'package:kernel/ast.dart';
 
 /// Returns a [Program] object containing empty definitions of core SDK classes.
 Program createMockSdkProgram() {
-  var coreLib = new Library(Uri.parse('dart:core'));
-  var asyncLib = new Library(Uri.parse('dart:async'));
-  var internalLib = new Library(Uri.parse('dart:_internal'));
+  var coreLib = new Library(Uri.parse('dart:core'), name: 'dart.core');
+  var asyncLib = new Library(Uri.parse('dart:async'), name: 'dart.async');
+  var internalLib =
+      new Library(Uri.parse('dart:_internal'), name: 'dart._internal');
 
   Class addClass(Library lib, Class c) {
     lib.addClass(c);
     return c;
   }
 
   var objectClass = addClass(coreLib, new Class(name: 'Object'));
   var objectType = objectClass.rawType;
 
   TypeParameter typeParam(String name, [DartType bound]) {
@@ skipping 35 matching lines @@
   addClass(coreLib, class_('Symbol'));
   addClass(coreLib, class_('Type'));
   addClass(coreLib, class_('Function'));
   addClass(coreLib, class_('Invocation'));
   addClass(asyncLib, class_('Future', typeParameters: [typeParam('T')]));
   addClass(asyncLib, class_('Stream', typeParameters: [typeParam('T')]));
   addClass(internalLib, class_('Symbol'));
 
   return new Program([coreLib, asyncLib, internalLib]);
 }