dart2js: get:hashCode methods to avoid Object.hashCode

pkg/compiler/lib/src/tree/nodes.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.
 
 import 'dart:collection' show IterableMixin;
 
 import '../common.dart';
 import '../elements/elements.dart' show MetadataAnnotation;
 import '../resolution/secret_tree_element.dart'
     show NullTreeElementMixin, StoredTreeElementMixin;
@@ skipping 277 matching lines @@
  *
  * The abstract part of "abstract syntax tree" is invalidated when
  * supporting tools such as code formatting. These tools need concrete
  * syntax such as parentheses and no constant folding.
  *
  * We support these tools by storing additional references back to the
  * token stream. These references are stored in fields ending with
  * "Token".
  */
 abstract class Node extends NullTreeElementMixin implements Spannable {
-  final int hashCode;
+  final int hashCode = _HASH_COUNTER = (_HASH_COUNTER + 1).toUnsigned(30);
   static int _HASH_COUNTER = 0;
 
-  Node() : hashCode = ++_HASH_COUNTER;
+  Node();
 
   accept(Visitor visitor);
 
   accept1(Visitor1 visitor, arg);
 
   visitChildren(Visitor visitor);
 
   visitChildren1(Visitor1 visitor, arg);
 
   /**
@@ skipping 2814 matching lines @@
 
   // VariableDefinitions.
   get metadata => null;
   get type => null;
 
   // Typedef.
   get typeParameters => null;
   get formals => null;
   get typedefKeyword => null;
 }