Remove one more use of mirrors: Components now have to explicitly sync their fields.

sky/sdk/lib/framework/components2/fixed_height_scrollable.dart

Index: sky/sdk/lib/framework/components2/fixed_height_scrollable.dart
diff --git a/sky/sdk/lib/framework/components2/fixed_height_scrollable.dart b/sky/sdk/lib/framework/components2/fixed_height_scrollable.dart
index e3becda0128d251a40d925fc39ba52b8e2952ec5..5a52010f8c4d14fc0c1eb9d83ebc452b0cab9315 100644
--- a/sky/sdk/lib/framework/components2/fixed_height_scrollable.dart
+++ b/sky/sdk/lib/framework/components2/fixed_height_scrollable.dart
@@ -10,16 +10,21 @@ import 'package:vector_math/vector_math.dart';
 import 'scrollable.dart';
 
 abstract class FixedHeightScrollable extends Scrollable {
+
   FixedHeightScrollable({ this.itemHeight, Object key }) : super(key: key) {
     assert(itemHeight != null);
   }
 
+  double itemHeight;
+
+  void syncFields(FixedHeightScrollable source) {
+    itemHeight = source.itemHeight;
+    super.syncFields(source);
+  }
+
   ScrollBehavior createScrollBehavior() => new OverscrollBehavior();
   OverscrollBehavior get scrollBehavior => super.scrollBehavior as OverscrollBehavior;
 
-  double _height;
-  final double itemHeight;
-
   int _itemCount = 0;
   int get itemCount => _itemCount;
   void set itemCount (int value) {
@@ -29,6 +34,7 @@ abstract class FixedHeightScrollable extends Scrollable {
     }
   }
 
+  double _height;
   void _handleSizeChanged(Size newSize) {
     setState(() {
       _height = newSize.height;
@@ -37,24 +43,24 @@ abstract class FixedHeightScrollable extends Scrollable {
   }
 
   UINode buildContent() {
-    var itemNumber = 0;
-    var itemCount = 0;
+    var itemShowIndex = 0;
+    var itemShowCount = 0;
 
     Matrix4 transform = new Matrix4.identity();
 
     if (_height != null && _height > 0.0) {
       if (scrollOffset < 0.0) {
         double visibleHeight = _height + scrollOffset;
-        itemCount = (visibleHeight / itemHeight).round() + 1;
+        itemShowCount = (visibleHeight / itemHeight).round() + 1;
         transform.translate(0.0, -scrollOffset);
       } else {
-        itemCount = (_height / itemHeight).ceil() + 1;
+        itemShowCount = (_height / itemHeight).ceil() + 1;
         double alignmentDelta = -scrollOffset % itemHeight;
         if (alignmentDelta != 0.0)
           alignmentDelta -= itemHeight;
 
         double drawStart = scrollOffset + alignmentDelta;
-        itemNumber = math.max(0, (drawStart / itemHeight).floor());
+        itemShowIndex = math.max(0, (drawStart / itemHeight).floor());
 
         transform.translate(0.0, alignmentDelta);
       }
@@ -70,7 +76,7 @@ abstract class FixedHeightScrollable extends Scrollable {
           child: new Transform(
             transform: transform,
             child: new BlockContainer(
-              children: buildItems(itemNumber, itemCount))
+              children: buildItems(itemShowIndex, itemShowCount))
           )
         )
       )
@@ -78,4 +84,5 @@ abstract class FixedHeightScrollable extends Scrollable {
   }
 
   List<UINode> buildItems(int start, int count);  
+
 }