Generate mock libraries and assert that helpers are non-null.

tests/compiler/dart2js/size_test.dart

 // Copyright (c) 2013, 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:expect/expect.dart';
 import "package:async_helper/async_helper.dart";
 import "compiler_helper.dart";
 
 const String TEST = "main() => [];";
 
-const String DEFAULT_CORELIB_WITH_LIST = r'''
-  class Object {
-    Object();
-  }
-  class bool {}
-  abstract class List {}
-  class num {}
-  class int {}
-  class double {}
-  class String {}
-  class Function {}
-  class Null {}
-  class Type {}
-  class Map {}
-  class StackTrace {}
-  identical(a, b) => true;
-  const proxy = 0;
-''';
+const Map<String, String> DEFAULT_CORELIB_WITH_LIST = const <String, String>{
+  'Object': 'class Object { Object(); }',
+  'bool': 'class bool {}',
+  'List': 'abstract class List {}',
+  'num': 'class num {}',
+  'int': 'class int {}',
+  'double': 'class double {}',
+  'String': 'class String {}',
+  'Function': 'class Function {}',
+  'Null': 'class Null {}',
+  'Type': 'class Type {}',
+  'Map': 'class Map {}',
+  'StackTrace': 'class StackTrace {}',
+  'identical': 'identical(a, b) => true;',
+  'proxy': 'const proxy = 0;',
+};
 
 main() {
   asyncTest(() => compileAll(TEST, coreSource: DEFAULT_CORELIB_WITH_LIST).
       then((generated) {
     return MockCompiler.create((MockCompiler compiler) {
       var backend = compiler.backend;
 
       // Make sure no class is emitted.
       Expect.isFalse(generated.contains(backend.emitter.finishClassesName));
     });
   }));
 }