Make unit testing of the compiler work with the new isolate helper library.

tests/compiler/dart2js/mock_compiler.dart

 // Copyright (c) 2012, 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 mock_compiler;
 
 import 'dart:uri';
 
 import '../../../sdk/lib/_internal/compiler/compiler.dart' as api;
 import '../../../sdk/lib/_internal/compiler/implementation/dart2jslib.dart'
@@ skipping 71 matching lines @@
   class Object {}
   class Type {}
   class Function {}
   class List<E> {}
   abstract class Map<K,V> {}
   class Closure {}
   class Null {}
   class Dynamic_ {}
   bool identical(Object a, Object b) {}''';
 
+const String DEFAULT_ISOLATE_HELPERLIB = r'''
+  class _WorkerBase {}''';
+
 class MockCompiler extends Compiler {
   List<WarningMessage> warnings;
   List<WarningMessage> errors;
   final Map<String, SourceFile> sourceFiles;
   Node parsedTree;
 
   MockCompiler({String coreSource: DEFAULT_CORELIB,
                 String helperSource: DEFAULT_HELPERLIB,
                 String interceptorsSource: DEFAULT_INTERCEPTORSLIB,
+                String isolateHelperSource: DEFAULT_ISOLATE_HELPERLIB,
                 bool enableTypeAssertions: false,
                 bool enableMinification: false,
                 bool enableConcreteTypeInference: false,
                 bool analyzeAll: false})
       : warnings = [], errors = [],
         sourceFiles = new Map<String, SourceFile>(),
         super(enableTypeAssertions: enableTypeAssertions,
               enableMinification: enableMinification,
               enableConcreteTypeInference: enableConcreteTypeInference,
               analyzeAll: analyzeAll) {
     coreLibrary = createLibrary("core", coreSource);
     // We need to set the assert method to avoid calls with a 'null'
     // target being interpreted as a call to assert.
     jsHelperLibrary = createLibrary("helper", helperSource);
     importHelperLibrary(coreLibrary);
     libraryLoader.importLibrary(jsHelperLibrary, coreLibrary, null);
 
     assertMethod = jsHelperLibrary.find(buildSourceString('assert'));
     interceptorsLibrary = createLibrary("interceptors", interceptorsSource);
+    isolateHelperLibrary = createLibrary("isolate_helper", isolateHelperSource);
 
     mainApp = mockLibrary(this, "");
     initializeSpecialClasses();
     // We need to make sure the Object class is resolved. When registering a
     // dynamic invocation the ArgumentTypesRegistry eventually iterates over
     // the interfaces of the Object class which would be 'null' if the class
     // wasn't resolved.
     objectClass.ensureResolved(this);
   }
 
@@ skipping 143 matching lines @@
   operator []=(Node node, Element element) {
     map[node] = element;
   }
 
   operator [](Node node) => map[node];
 
   void remove(Node node) {
     map.remove(node);
   }
 }