Fix hints reported by analyzer.

pkg/compiler/lib/src/js/js.dart

 // Copyright (c) 2015, 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;
 
 import 'package:js_ast/js_ast.dart';
 
 import '../common.dart';
 import '../compiler.dart' show Compiler;
@@ skipping 111 matching lines @@
   markSeen(TokenCounter visitor);
 }
 
 /// Represents the LiteralString resulting from unparsing [expression]. The
 /// actual unparsing is done on demand when requesting the [value] of this
 /// node.
 ///
 /// This is used when generated code needs to be represented as a string,
 /// for example by the lazy emitter or when generating code generators.
 class UnparsedNode extends DeferredString implements AstContainer {
-  @override
   final Node tree;
   final Compiler _compiler;
   final bool _protectForEval;
   LiteralString _cachedLiteral;
 
   Iterable<Node> get containedNodes => [tree];
 
   /// A [js.Literal] that represents the string result of unparsing [ast].
   ///
   /// When its string [value] is requested, the node pretty-prints the given
@@ skipping 44 matching lines @@
   }
   if (node is PropertyAccess) {
     PropertyAccess access = node;
     if (access.receiver is InterpolatedExpression) {
       InterpolatedExpression hole = access.receiver;
       return hole.isPositional && hole.nameOrPosition == 0;
     }
   }
   return false;
 }