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

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

Index: sky/sdk/lib/framework/widgets/fixed_height_scrollable.dart
diff --git a/sky/sdk/lib/framework/components2/fixed_height_scrollable.dart b/sky/sdk/lib/framework/widgets/fixed_height_scrollable.dart
similarity index 98%
rename from sky/sdk/lib/framework/components2/fixed_height_scrollable.dart
rename to sky/sdk/lib/framework/widgets/fixed_height_scrollable.dart
index 95392802c7dfdb8d0624ffa08a62e3d90c0cc1d3..70df8523d8d28039a319935c18c28f2f3ec2909c 100644
--- a/sky/sdk/lib/framework/components2/fixed_height_scrollable.dart
+++ b/sky/sdk/lib/framework/widgets/fixed_height_scrollable.dart
@@ -2,12 +2,13 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import '../animation/scroll_behavior.dart';
-import '../fn2.dart';
-import 'dart:async';
 import 'dart:math' as math;
+
 import 'package:vector_math/vector_math.dart';
+
+import '../animation/scroll_behavior.dart';
 import 'scrollable.dart';
+import 'wrappers.dart';
 
 abstract class FixedHeightScrollable extends Scrollable {