Begin to compute constant expressions in resolution.

tests/compiler/dart2js/mock_compiler.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 mock_compiler;
 
 import "package:expect/expect.dart";
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:compiler/compiler.dart' as api;
+import 'package:compiler/src/constants/expressions.dart';
 import 'package:compiler/src/elements/elements.dart';
 import 'package:compiler/src/js_backend/js_backend.dart'
     show JavaScriptBackend;
 import 'package:compiler/src/resolution/resolution.dart';
 import 'package:compiler/src/io/source_file.dart';
 import 'package:compiler/src/tree/tree.dart';
 import 'package:compiler/src/util/util.dart';
 import 'parser_helper.dart';
 
 import 'package:compiler/src/elements/modelx.dart'
@@ skipping 331 matching lines @@
 
   operator []=(Node node, Element element) {
     map[node] = element;
   }
 
   operator [](Node node) => map[node];
 
   void remove(Node node) {
     map.remove(node);
   }
+
+  List<ConstantExpression> get constants {
+    List<ConstantExpression> list = <ConstantExpression>[];
+    forEachConstantNode((_, c) => list.add(c));
+    return list;
+  }
 }
 
 // The mock compiler does not split the program in output units.
 class MockDeferredLoadTask extends DeferredLoadTask {
   MockDeferredLoadTask(Compiler compiler) : super(compiler);
 
   OutputUnit getElementOutputUnit(dynamic dependency) {
     return mainOutputUnit;
   }
 }
@@ skipping 20 matching lines @@
   MockElement(Element enclosingElement)
       : super('', ElementKind.FUNCTION, Modifiers.EMPTY,
               enclosingElement);
 
   get node => null;
 
   parseNode(_) => null;
 
   bool get hasNode => false;
 }