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';
 
 /// Generate a Lisp-like S-expression representation of an IR node as a string.
@@ skipping 14 matching lines @@
           String name = p.hint.name;
           names[p] = name;
           return name;
         })
         .join(' ');
     String body = indentBlock(() => visit(node.body));
     return '$indentation(FunctionDefinition $name ($parameters return)\n'
            '$body)';
   }
 
+  String visitFieldDefinition(FieldDefinition node) {
+    String name = node.element.name;
+    names[node.returnContinuation] = 'return';
+    String body = indentBlock(() => visit(node.body));
+    return '$indentation(FieldDefinition $name (return)\n'
+           '$body)';
+  }
+
   String visitLetPrim(LetPrim node) {
     String name = newValueName();
     names[node.primitive] = name;
     String value = visit(node.primitive);
     String body = visit(node.body);
     return '$indentation(LetPrim $name $value)\n$body';
   }
 
   String visitLetCont(LetCont node) {
     String cont = newContinuationName();
@@ skipping 144 matching lines @@
     return '$indentation(DeclareFunction ${node.variable.name} =\n'
            '$function in\n'
            '$body)';
   }
 
   String visitIsTrue(IsTrue node) {
     String value = names[node.value.definition];
     return '(IsTrue $value)';
   }
 }