Factor ScrollCurve out of Scrollable

sky/framework/components/fixed_height_scrollable.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 '../animation/scroll_curve.dart';
 import '../fn.dart';
 import 'dart:sky' as sky;
 import 'scrollable.dart';
 
 abstract class FixedHeightScrollable extends Scrollable {
   // TODO(rafaelw): This component really shouldn't have an opinion
   // about how it is sized. The owning component should decide whether
   // it's explicitly sized or flexible or whatever...
   static final Style _style = new Style('''
     overflow: hidden;
     position: relative;
     flex: 1;
     will-change: transform;'''
   );
 
   static final Style _scrollAreaStyle = new Style('''
     position:relative;
     will-change: transform;'''
   );
 
   double _height = 0.0;
   double _itemHeight;
 
   FixedHeightScrollable({
     Object key,
-    double minOffset,
-    double maxOffset
-  }) : super(key: key, minOffset: minOffset, maxOffset: maxOffset) {
-  }
+    ScrollCurve scrollCurve
+  }) : super(key: key, scrollCurve: scrollCurve);
 
   void didMount() {
     super.didMount();
     var root = getRoot();
     var item = root.firstChild.firstChild;
     sky.ClientRect scrollRect = root.getBoundingClientRect();
     sky.ClientRect itemRect = item.getBoundingClientRect();
     assert(scrollRect.height > 0);
     assert(itemRect.height > 0);
 
@@ skipping 27 matching lines @@
       children: [
         new Container(
           styles: [_scrollAreaStyle],
           inlineStyle: transformStyle,
           children: buildItems(itemNumber, drawCount)
         )
       ]
     );
   }
 }