fix implicit_scope_test and builtin_identifier_test

lib/src/js/printer.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_ast;
 
 
 class JavaScriptPrintingOptions {
   final bool shouldCompressOutput;
   final bool minifyLocalVariables;
@@ skipping 220 matching lines @@
     } else {
       lineOut();
     }
     indentMore();
     visit(body);
     indentLess();
     return false;
   }
 
   void blockOutWithoutBraces(Node node) {
-    if (node is Block) {
+    if (node is Block && !node.isScope) {
       context.enterNode(node);
       Block block = node;
       block.statements.forEach(blockOutWithoutBraces);
       context.exitNode(node);
     } else {
       visit(node);
     }
   }
 
   void blockOut(Block node, bool shouldIndent, bool needsNewline) {
@@ skipping 1245 matching lines @@
     declare(node.name);
     node.function.accept(this);
   }
 
   visitClassExpression(ClassExpression node) {
     declare(node.name);
     if (node.heritage != null) node.heritage.accept(this);
     for (Method element in node.methods) element.accept(this);
   }
 }