dart2dart: Bugfix in copy propagator.

pkg/compiler/lib/src/tree_ir/tree_ir_nodes.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 tree_ir_nodes;
 
 import '../constants/expressions.dart';
 import '../constants/values.dart' as values;
 import '../dart_types.dart' show DartType, GenericType, TypeVariableType;
 import '../elements/elements.dart';
@@ skipping 98 matching lines @@
   /// Number of places where this variable occurs in a [VariableUse].
   int readCount = 0;
 
   /// Number of places where this variable occurs as:
   /// - left-hand of an [Assign]
   /// - left-hand of a [FunctionDeclaration]
   /// - parameter in a [FunctionDefinition]
   /// - catch parameter in a [Try]
   int writeCount = 0;
 
+  /// True if a nested function reads or writes this variable.
+  ///
+  /// Always false in JS-mode because closure conversion eliminated nested
+  /// functions.
+  bool isCaptured = false;
+
   Variable(this.host, this.element) {
     assert(host != null);
   }
 }
 
 /// Read the value of a variable.
 class VariableUse extends Expression {
   Variable variable;
 
   /// Creates a use of [variable] and updates its `readCount`.
@@ skipping 903 matching lines @@
   }
 
   visitReifyRuntimeType(ReifyRuntimeType node) {
     visitExpression(node.value);
   }
 
   visitReadTypeVariable(ReadTypeVariable node) {
     visitExpression(node.target);
   }
 }