MutableVariable no longer has a host Element.

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.
 
 // IrNodes are kept in a separate library to have precise control over their
 // dependencies on other parts of the system.
 library dart2js.ir_nodes;
 
 import '../constants/expressions.dart';
 import '../constants/values.dart' as values show ConstantValue;
@@ skipping 845 matching lines @@
   FieldDefinition.withoutInitializer(this.element)
       : this.body = null;
 
   accept(Visitor visitor) => visitor.visitFieldDefinition(this);
 
   bool get isEmpty => body == null;
 }
 
 /// Identifies a mutable variable.
 class MutableVariable extends Definition {
-  /// Body of source code that declares this mutable variable.
-  ExecutableElement host;
   Entity hint;
 
-  MutableVariable(this.host, this.hint);
+  MutableVariable(this.hint);
 
   accept(Visitor v) => v.visitMutableVariable(this);
 }
 
 class Body extends InteriorNode {
   Expression body;
   final Continuation returnContinuation;
   Body(this.body, this.returnContinuation);
   accept(Visitor visitor) => visitor.visitBody(this);
 }
@@ skipping 528 matching lines @@
     processNonTailThrow(node);
     processReference(node.value);
   }
 
   processCreateInvocationMirror(CreateInvocationMirror node) {}
   visitCreateInvocationMirror(CreateInvocationMirror node) {
     processCreateInvocationMirror(node);
     node.arguments.forEach(processReference);
   }
 }