dart2js: get:hashCode methods to avoid Object.hashCode

pkg/compiler/lib/src/closure.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.
 
 library closureToClassMapper;
 
 import 'common.dart';
 import 'common/names.dart' show Identifiers;
 import 'common/resolution.dart' show ParsingContext, Resolution;
 import 'common/tasks.dart' show CompilerTask;
@@ skipping 237 matching lines @@
     return visitor.visitClosureClassElement(this, arg);
   }
 }
 
 /// A local variable that contains the box object holding the [BoxFieldElement]
 /// fields.
 class BoxLocal extends Local {
   final String name;
   final ExecutableElement executableContext;
 
+  final int hashCode = _nextHashCode = (_nextHashCode + 10007).toUnsigned(30);
+  static int _nextHashCode = 0;
+
   BoxLocal(this.name, this.executableContext);
 
   String toString() => 'BoxLocal($name)';
 }
 
 // TODO(ngeoffray, ahe): These classes continuously cause problems.  We need to
 // find a more general solution.
 class BoxFieldElement extends ElementX
     implements
         TypedElement,
@@ skipping 51 matching lines @@
   @override
   bool get hasConstant => false;
 
   @override
   ConstantExpression get constant => null;
 }
 
 /// A local variable used encode the direct (uncaptured) references to [this].
 class ThisLocal extends Local {
   final ExecutableElement executableContext;
-  final hashCode = ++ElementX.elementHashCode;
+  final hashCode = ElementX.newHashCode();
 
   ThisLocal(this.executableContext);
 
   String get name => 'this';
 
   ClassElement get enclosingClass => executableContext.enclosingClass;
 }
 
 /// Call method of a closure class.
 class SynthesizedCallMethodElementX extends BaseFunctionElementX
@@ skipping 849 matching lines @@
 ///
 /// Move the below classes to a JS model eventually.
 ///
 abstract class JSEntity implements Entity {
   Entity get declaredEntity;
 }
 
 abstract class PrivatelyNamedJSEntity implements JSEntity {
   Entity get rootOfScope;
 }