Support abstract getters without parameters.

dart/tests/compiler/dart2js_foreign/native_property_test.dart

 // Copyright (c) 2011, 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.
 
 // Properties on hidden native classes.
 
 @native("*A")
 class A  {
 
   // Setters and getters should be similar to these methods:
   @native('return this._x;')
   int getX();
 
   @native('this._x = value;')
   void setX(int value);
 
   @native
-  int get X();
+  int get X;
 
   @native
   set X(int value);
 
   @native
-  int get Y();
+  int get Y;
 
   @native
   set Y(int value);
 
   @native('return this._z;')
-  int get Z();
+  int get Z;
 
   @native('this._z = value;')
   set Z(int value);
 }
 
 @native
 A makeA() { return new A(); }
 
 @native("""
 function A() {}
@@ skipping 17 matching lines @@
   Expect.equals(5, a.getX());
 
   a.X = 10;
   a.Y = 20;
   a.Z = 30;
 
   Expect.equals(10, a.X);
   Expect.equals(20, a.Y);
   Expect.equals(30, a.Z);
 }