Refactor fn2.dart, since it breached our 1000-line threshold.

sky/sdk/lib/framework/widgets/popup_menu.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 import 'dart:async';
 import 'dart:math' as math;
 import 'dart:sky' as sky;
 
 import '../animation/animated_value.dart';
-import '../fn2.dart';
 import '../painting/box_painter.dart';
 import '../theme2/colors.dart';
 import '../theme2/shadows.dart';
 import 'animated_component.dart';
 import 'material.dart';
 import 'popup_menu_item.dart';
+import 'wrappers.dart';
 
 const double _kMenuOpenDuration = 300.0;
 const double _kMenuCloseDuration = 200.0;
 const double _kMenuCloseDelay = 100.0;
 
 enum MenuState { hidden, opening, open, closing }
 
 class PopupMenuController {
   AnimatedValue position = new AnimatedValue(0.0);
   MenuState _state = MenuState.hidden;
@@ skipping 83 matching lines @@
           child: new Container(
             padding: const EdgeDims.all(8.0),
             child: new Block(children)
           )
         )
       )
     );
   }
 
 }