Store toString value in enum.

pkg/compiler/lib/src/js_backend/namer.dart

 // Copyright (c) 2011, 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 js_backend.namer;
 
 import 'dart:collection' show HashMap;
 
 import 'package:js_runtime/shared/embedded_names.dart' show JsGetName;
 
@@ skipping 1863 matching lines @@
     } else {
       // Using some bits from the keys hash tag groups the names Maps with the
       // same structure.
       add(getHashTag(constant.keyList, 2) + getHashTag(constant, 3));
     }
   }
 
   @override
   void visitConstructed(ConstructedConstantValue constant, [_]) {
     addRoot(constant.type.element.name);
+
+    // Recognize enum constants and only include the index.
+    final Map<FieldEntity, ConstantValue> fieldMap = constant.fields;
+    int size = fieldMap.length;
+    if (size == 1 || size == 2) {
+      FieldEntity indexField;
+      for (FieldEntity field in fieldMap.keys) {
+        String name = field.name;
+        if (name == 'index') {
+          indexField = field;
+        } else if (name == '_name') {
+          // Ingore _name field.
+        } else {
+          indexField = null;
+          break;
+        }
+      }
+      if (indexField != null) {
+        _visit(constant.fields[indexField]);
+        return;
+      }
+    }
+
     // TODO(johnniwinther): This should be accessed from a codegen closed world.
     codegenWorldBuilder.forEachInstanceField(constant.type.element,
         (_, FieldElement field) {
       if (failed) return;
       _visit(constant.fields[field]);
     });
   }
 
   @override
   void visitType(TypeConstantValue constant, [_]) {
@@ skipping 306 matching lines @@
   void addSuggestion(String original, String suggestion) {
     assert(!_suggestedNames.containsKey(original));
     _suggestedNames[original] = suggestion;
   }
 
   bool hasSuggestion(String original) => _suggestedNames.containsKey(original);
   bool isSuggestion(String candidate) {
     return _suggestedNames.containsValue(candidate);
   }
 }