Handle const Symbol(...) in kernel_impact

pkg/compiler/lib/src/kernel/native_basic_data.dart

 // Copyright (c) 2017, 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.
 
 // TODO(johnniwinther): Make this a separate library.
 part of dart2js.kernel.element_map;
 
 class KernelAnnotationProcessor implements AnnotationProcessor {
   final KernelToElementMap elementMap;
 
   KernelAnnotationProcessor(this.elementMap);
 
   void extractNativeAnnotations(
       LibraryEntity library, NativeBasicDataBuilder nativeBasicDataBuilder) {
     ElementEnvironment elementEnvironment = elementMap.elementEnvironment;
     CommonElements commonElements = elementMap.commonElements;
 
     elementEnvironment.forEachClass(library, (ClassEntity cls) {
       String annotationName;
       // TODO(johnniwinther): Make [_getClassMetadata] public and at test to
       // guard against misuse.
-      for (ConstantExpression annotation in elementMap._getClassMetadata(cls)) {
-        ConstantValue value =
-            elementMap.constantEnvironment.getConstantValue(annotation);
+      for (ConstantValue value in elementMap._getClassMetadata(cls)) {
         String name = readAnnotationName(
             cls, value, commonElements.nativeAnnotationClass);
         if (annotationName == null) {
           annotationName = name;
         } else if (name != null) {
           throw new SpannableAssertionFailure(
               cls, 'Too many name annotations.');
         }
       }
       if (annotationName != null) {
         nativeBasicDataBuilder.setNativeClassTagInfo(cls, annotationName);
       }
     });
   }
 
   void extractJsInteropAnnotations(
       LibraryEntity library, NativeBasicDataBuilder nativeBasicDataBuilder) {
     // TODO(johnniwinther): Implement this.
   }
 
   @override
   void processJsInteropAnnotations(
       NativeBasicData nativeData, NativeDataBuilder nativeDataBuilder) {
     // TODO(johnniwinther): Implement this.
   }
 }