Refactor ConstantExpression/ConstantConstructor to use entities.

tests/compiler/dart2js/serialization/equivalence_test.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 dart2js.serialization_test;
 
 import 'dart:io';
 import '../memory_compiler.dart';
 import 'package:async_helper/async_helper.dart';
 import 'package:compiler/src/commandline_options.dart';
 import 'package:compiler/src/common.dart';
 import 'package:compiler/src/common/resolution.dart';
 import 'package:compiler/src/constants/constructors.dart';
 import 'package:compiler/src/compiler.dart';
 import 'package:compiler/src/diagnostics/invariant.dart';
 import 'package:compiler/src/elements/elements.dart';
+import 'package:compiler/src/elements/resolution_types.dart';
 import 'package:compiler/src/elements/visitor.dart';
 import 'package:compiler/src/filenames.dart';
 import 'package:compiler/src/library_loader.dart';
 import 'package:compiler/src/ordered_typeset.dart';
 import 'package:compiler/src/serialization/element_serialization.dart';
 import 'package:compiler/src/serialization/equivalence.dart';
 import 'package:compiler/src/serialization/json_serializer.dart';
 import 'package:compiler/src/serialization/serialization.dart';
 import 'package:expect/expect.dart';
 import 'test_helper.dart';
@@ skipping 171 matching lines @@
       ConstantConstructor constructor1, ConstantConstructor constructor2) {
     if (identical(constructor1, constructor2)) return;
     check(constructor1, constructor2, 'kind', constructor1.kind,
         constructor2.kind);
     constructor1.accept(this, constructor2);
   }
 
   @override
   visitGenerative(GenerativeConstantConstructor constructor1,
       GenerativeConstantConstructor constructor2) {
-    checkTypes(constructor1, constructor2, 'type', constructor1.type,
-        constructor2.type);
+    ResolutionInterfaceType type1 = constructor1.type;
+    ResolutionInterfaceType type2 = constructor2.type;
+    checkTypes(constructor1, constructor2, 'type', type1, type2);
     check(constructor1, constructor2, 'defaultValues.length',
         constructor1.defaultValues.length, constructor2.defaultValues.length);
     constructor1.defaultValues.forEach((k, v) {
       checkConstants(constructor1, constructor2, 'defaultValue[$k]', v,
           constructor2.defaultValues[k]);
     });
     check(constructor1, constructor2, 'fieldMap.length',
         constructor1.fieldMap.length, constructor2.fieldMap.length);
     constructor1.fieldMap.forEach((k1, v1) {
       bool matched = false;
@@ skipping 614 matching lines @@
     });
   }
 
   @override
   void visitErroneousElement(
       ErroneousElement element1, ErroneousElement element2) {
     check(element1, element2, 'messageKind', element1.messageKind,
         element2.messageKind);
   }
 }