Remove ConstantExpression.value

pkg/compiler/lib/src/cps_ir/cps_ir_nodes_sexpr.dart

 // Copyright (c) 2014, 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.ir_nodes_sexpr;
 
 import '../constants/values.dart';
 import '../util/util.dart';
 import 'cps_ir_nodes.dart';
 
@@ skipping 185 matching lines @@
   }
 
   String visitBranch(Branch node) {
     String condition = visit(node.condition);
     String trueCont = access(node.trueContinuation);
     String falseCont = access(node.falseContinuation);
     return '$indentation(Branch $condition $trueCont $falseCont)';
   }
 
   String visitConstant(Constant node) {
-    String value =
-        node.expression.value.accept(new ConstantStringifier(), null);
+    String value = node.value.accept(new ConstantStringifier(), null);
     return '(Constant $value)';
   }
 
   String visitCreateFunction(CreateFunction node) {
     String function =
         indentBlock(() => indentBlock(() => visit(node.definition)));
     return '(CreateFunction\n$function)';
   }
 
   String visitContinuation(Continuation node) {
@@ skipping 220 matching lines @@
   void setReturnContinuation(Continuation node) {
     assert(!_names.containsKey(node) || _names[node] == 'return');
     _names[node] = 'return';
   }
 
   String getName(Node node) {
     if (!_names.containsKey(node)) return 'MISSING_NAME';
     return _names[node];
   }
 }