Update status for minified and fix a type warning

dart/sdk/lib/_internal/compiler/implementation/resolution/members.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 resolution;
 
 abstract class TreeElements {
   Element get currentElement;
   Set<Node> get superUses;
 
@@ skipping 2574 matching lines @@
 
     if (node.isConst() && isSymbolConstructor) {
       Node argumentNode = node.send.arguments.head;
       Constant name = compiler.metadataHandler.compileNodeWithDefinitions(
           argumentNode, mapping, isConst: true);
       if (!name.isString()) {
         DartType type = name.computeType(compiler);
         compiler.reportErrorCode(argumentNode, MessageKind.STRING_EXPECTED,
                                  {'type': type});
       } else {
-        validateSymbol(argumentNode, name.toDartString().slowToString());
+        StringConstant stringConstant = name;
+        validateSymbol(argumentNode,
+                       stringConstant.toDartString().slowToString());
       }
     }
 
     return null;
   }
 
   void validateSymbol(Node node, String name) {
     if (name.isEmpty) return;
     if (name.startsWith('_')) {
       compiler.reportErrorCode(node, MessageKind.PRIVATE_IDENTIFIER,
@@ skipping 1349 matching lines @@
     return e;
   }
 
   /// Assumed to be called by [resolveRedirectingFactory].
   Element visitReturn(Return node) {
     Node expression = node.expression;
     return finishConstructorReference(visit(expression),
                                       expression, expression);
   }
 }