dart2js: Change how super tear-offs are registered.

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/values.dart' as values;
 import '../dart_types.dart' show DartType, InterfaceType, TypeVariableType;
 import '../elements/elements.dart';
 import '../io/source_information.dart' show SourceInformation;
@@ skipping 218 matching lines @@
 class InvokeMethodDirectly extends Expression implements Invoke {
   Expression receiver;
   final Element target;
   final Selector selector;
   final List<Expression> arguments;
   final SourceInformation sourceInformation;
 
   InvokeMethodDirectly(this.receiver, this.target, this.selector,
       this.arguments, this.sourceInformation);
 
+  bool get isTearOff => selector.isGetter && !target.isGetter;
+
   accept(ExpressionVisitor visitor) => visitor.visitInvokeMethodDirectly(this);
   accept1(ExpressionVisitor1 visitor, arg) {
     return visitor.visitInvokeMethodDirectly(this, arg);
   }
 }
 
 /**
  * Call to a factory or generative constructor.
  */
 class InvokeConstructor extends Expression implements Invoke {
@@ skipping 1347 matching lines @@
 
   /// Number of uses of the current fallthrough target.
   int get useCount => _stack.last.useCount;
 
   /// Indicate that a statement will fall through to the current fallthrough
   /// target.
   void use() {
     ++_stack.last.useCount;
   }
 }