Add support for fields to the new dart backend.

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 '../util/util.dart';
 import 'cps_ir_nodes.dart';
 
 /// A [Decorator] is a function used by [SExpressionStringifier] to augment the
@@ skipping 25 matching lines @@
 
   String visitFunctionDefinition(FunctionDefinition node) {
     String name = node.element.name;
     namer.useReturnName(node.returnContinuation);
     String parameters = node.parameters.map(visit).join(' ');
     String body = indentBlock(() => visit(node.body));
     return '$indentation(FunctionDefinition $name ($parameters return)\n'
            '$body)';
   }
 
+  String visitFieldDefinition(FieldDefinition node) {
+    String name = node.element.name;
+    namer.useReturnName(node.returnContinuation);
+    String body = indentBlock(() => visit(node.body));
+    return '$indentation(FieldDefinition $name (return)\n'
+           '$body)';
+  }
+
   String visitLetPrim(LetPrim node) {
     String name = newValueName(node.primitive);
     String value = visit(node.primitive);
     String body = visit(node.body);
     return '$indentation(LetPrim $name $value)\n$body';
   }
 
   String visitLetCont(LetCont node) {
     String cont = newContinuationName(node.continuation);
     // TODO(karlklose): this should be changed to `.map(visit).join(' ')`  and
@@ skipping 172 matching lines @@
   String useReturnName(Continuation node) {
     assert(!_names.containsKey(node) || _names[node] == 'return');
     return _names[node] = 'return';
   }
 
   String getName(Node node) {
     assert(_names.containsKey(node));
     return _names[node];
   }
 }