Remove redundant setState() calls around scroll behaviour updates.

sky/sdk/lib/widgets/variable_height_scrollable.dart

Index: sky/sdk/lib/widgets/variable_height_scrollable.dart
diff --git a/sky/sdk/lib/widgets/variable_height_scrollable.dart b/sky/sdk/lib/widgets/variable_height_scrollable.dart
index eee82dda1ef4c1c086693f73da46d807a9b638b3..ed74d11ca23f2cd84a792586b27d42124c5e77f7 100644
--- a/sky/sdk/lib/widgets/variable_height_scrollable.dart
+++ b/sky/sdk/lib/widgets/variable_height_scrollable.dart
@@ -30,16 +30,15 @@ class VariableHeightScrollable extends Scrollable {
   OverscrollBehavior get scrollBehavior => super.scrollBehavior;
 
   void _handleSizeChanged(Size newSize) {
-    setState(() {
-      scrollBehavior.containerSize = newSize.height;
-    });
+    scrollBehavior.containerSize = newSize.height;

[hansmuller, 2015/07/13 19:03:53]

If the viewport's size changes, don't you want to layout/paint?

   }
 
   void _handleLayoutChanged(
-      int firstVisibleChildIndex,
-      int visibleChildCount,
-      UnmodifiableListView<double> childOffsets,
-      bool didReachLastChild) {
+    int firstVisibleChildIndex,
+    int visibleChildCount,
+    UnmodifiableListView<double> childOffsets,
+    bool didReachLastChild
+  ) {
     assert(childOffsets.length > 0);
     scrollBehavior.contentsSize = didReachLastChild ? childOffsets.last : double.INFINITY;
     if (didReachLastChild && scrollOffset > scrollBehavior.maxScrollOffset)