Make FloatingActionButton respect the onPressed ctor arg.

sky/sdk/lib/widgets/floating_action_button.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 'basic.dart';
 import 'button_base.dart';
 import 'ink_well.dart';
 import 'material.dart';
 import 'theme.dart';
 
 // TODO(eseidel): This needs to change based on device size?
 // http://www.google.com/design/spec/layout/metrics-keylines.html#metrics-keylines-keylines-spacing
 const double _kSize = 56.0;
 
 class FloatingActionButton extends ButtonBase {
 
   FloatingActionButton({
     String key,
     this.child,
-    Function onPressed
+    this.onPressed
   }) : super(key: key);
 
   Widget child;
   Function onPressed;
 
   void syncFields(FloatingActionButton source) {
     super.syncFields(source);
     child = source.child;
     onPressed = source.onPressed;
   }
@@ skipping 13 matching lines @@
             width: _kSize,
             height: _kSize,
             child: new InkWell(child: new Center(child: child))
           )
         )
       )
     );
   }
 
 }