Make mock_compiler initialize the identical function, and use the identical function element direct…

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 "package:expect/expect.dart";
 import 'dart:collection';
 import 'dart:uri';
 
@@ skipping 181 matching lines @@
     interceptorsLibrary = createLibrary("interceptors", interceptorsSource);
     isolateHelperLibrary = createLibrary("isolate_helper", isolateHelperSource);
 
     // Set up the library imports.
     importHelperLibrary(coreLibrary);
     libraryLoader.importLibrary(jsHelperLibrary, coreLibrary, null);
     libraryLoader.importLibrary(interceptorsLibrary, coreLibrary, null);
     libraryLoader.importLibrary(isolateHelperLibrary, coreLibrary, null);
 
     assertMethod = jsHelperLibrary.find(buildSourceString('assert'));
+    identicalFunction = coreLibrary.find(buildSourceString('identical'));
 
     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);
 
     // Our unit tests check code generation output that is affected by
@@ skipping 181 matching lines @@
   }
 }
 
 class MockDeferredLoadTask extends DeferredLoadTask {
   MockDeferredLoadTask(Compiler compiler) : super(compiler);
 
   void registerMainApp(LibraryElement mainApp) {
     // Do nothing.
   }
 }