Add missing parent pointers in CopyingVisitor

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

 // Copyright (c) 2013, 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;
 
 import 'dart:collection';
 import 'cps_fragment.dart' show CpsFragment;
 import '../constants/values.dart' as values;
 import '../dart_types.dart' show DartType, InterfaceType, TypeVariableType;
 import '../elements/elements.dart';
@@ skipping 2657 matching lines @@
   Expression _first = null;
   Expression _current = null;
 
   void plug(Expression body) {
     if (_first == null) {
       _first = body;
     } else {
       assert(_current != null);
       InteriorExpression interior = _current;
       interior.body = body;
+      body.parent = interior;
     }
     _current = body;
   }
 
   // Continuations are added to the visitor's stack to be visited after copying
   // the current block is finished.  The stack action saves the current block,
   // copies the continuation's body, sets the body on the copy of the
   // continuation, and restores the current block.
   //
   // Note that continuations are added to the copy map before the stack action
   // to visit them is performed.
   void push(Continuation cont) {
     assert(!cont.isReturnContinuation);
     _stack.add(() {
       Expression savedFirst = _first;
       _first = _current = null;
       _processBlock(cont.body);
-      _copies[cont].body = _first;
+      Continuation contCopy = _copies[cont];
+      contCopy.body = _first;
+      _first.parent = contCopy;
       _first = savedFirst;
       _current = null;
     });
   }
 
   FunctionDefinition copy(FunctionDefinition node) {
     assert(_first == null && _current == null);
     _first = _current = null;
     // Definitions are copied where they are bound, before processing
     // expressions in the scope of their binding.
@@ skipping 78 matching lines @@
     plug(new Branch.loose(_definitions.getCopy(node.condition),
         _copies[node.trueContinuation.definition],
         _copies[node.falseContinuation.definition])
       ..isStrictCheck = node.isStrictCheck);
   }
 
   visitUnreachable(Unreachable node) {
     plug(new Unreachable());
   }
 }