Support serialization of all resolved asts from dart:core

pkg/compiler/lib/src/js_backend/backend.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.
 
 part of js_backend;
 
 const VERBOSE_OPTIMIZER_HINTS = false;
 
 class JavaScriptItemCompilationContext extends ItemCompilationContext {
   final Set<HInstruction> boundsChecked = new Set<HInstruction>();
@@ skipping 601 matching lines @@
       // add both to the list of helpers.
       helpersUsed.add(element.implementation);
     }
     return element;
   }
 
   bool _isValidBackendUse(Element element) {
     assert(invariant(element, element.isDeclaration, message: ""));
     if (element == helpers.streamIteratorConstructor ||
         element == helpers.compiler.symbolConstructor ||
-        element == helpers.compiler.symbolValidatedConstructor ||
+        helpers.isSymbolValidatedConstructor(element) ||
         element == helpers.syncCompleterConstructor ||
         element == coreClasses.symbolClass ||
         element == helpers.objectNoSuchMethod) {
       // TODO(johnniwinther): These are valid but we could be more precise.
       return true;
     } else if (element.implementationLibrary.isPatch ||
         // Needed to detect deserialized injected elements, that is
         // element declared in patch files.
         (element.library.isPlatformLibrary &&
             element.sourcePosition.uri.path
@@ skipping 2343 matching lines @@
 
   @override
   void onImpactUsed(ImpactUseCase impactUse) {
     if (impactUse == DeferredLoadTask.IMPACT_USE && !supportSerialization) {
       // TODO(johnniwinther): Allow emptying when serialization has been
       // performed.
       resolution.emptyCache();
     }
   }
 }