Remove `Resource` from mock libraries.

tests/compiler/dart2js/mock_libraries.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 for creating mock versions of platform and internal libraries.
 
 library mock_libraries;
 
 const DEFAULT_PLATFORM_CONFIG = """
 [libraries]
@@ skipping 81 matching lines @@
   'print': 'print(var obj) {}',
   'proxy': 'const proxy = 0;',
   'Object': r'''
       class Object {
         const Object();
         operator ==(other) { return true; }
         get hashCode => throw "Object.hashCode not implemented.";
         String toString() { return null; }
         noSuchMethod(im) { throw im; }
       }''',
-  'Resource': 'class Resource {}',
   'StackTrace': 'abstract class StackTrace {}',
   'String': 'class String implements Pattern {}',
   'Symbol': '''
       abstract class Symbol { 
         const factory Symbol(String name) = internal.Symbol; 
       }
       ''',
   'Type': 'class Type {}',
   'Pattern': 'abstract class Pattern {}',
   '_genericNoSuchMethod': '_genericNoSuchMethod(a,b,c,d,e) {}',
@@ skipping 372 matching lines @@
 
     const LookupMap(this._entries, [this._nestedMaps = const []])
         : _key = null, _value = null;
 
     const LookupMap.pair(this._key, this._value)
         : _entries = const [], _nestedMaps = const [];
     V operator[](K k) => null;
   }''',
   '_version': 'const _version = "0.0.1+1";',
 };