BlockViewport didn't implement the intrinsic dimension functions correctly.

sky/sdk/lib/rendering/block.dart

Index: sky/sdk/lib/rendering/block.dart
diff --git a/sky/sdk/lib/rendering/block.dart b/sky/sdk/lib/rendering/block.dart
index 1573f3833744d54751c342fbe888ad69caf986a1..bc2b82e2042d8899f5985baab5ab9a2bf525880b 100644
--- a/sky/sdk/lib/rendering/block.dart
+++ b/sky/sdk/lib/rendering/block.dart
@@ -26,6 +26,50 @@ abstract class RenderBlockBase extends RenderBox with ContainerRenderObjectMixin
       child.parentData = new BlockParentData();
   }
 
+  double computeDistanceToActualBaseline(TextBaseline baseline) {
+    return defaultComputeDistanceToFirstActualBaseline(baseline);
+  }
+
+  double _childrenHeight;
+  double get childrenHeight => _childrenHeight;
+
+  void markNeedsLayout() {
+    _childrenHeight = null;
+    super.markNeedsLayout();
+  }
+
+  void performLayout() {
+    assert(constraints is BoxConstraints);
+    double width = constraints.constrainWidth(constraints.maxWidth);
+    BoxConstraints innerConstraints = _getInnerConstraintsForWidth(width);
+    double y = 0.0;
+    RenderBox child = firstChild;
+    while (child != null) {
+      child.layout(innerConstraints, parentUsesSize: true);
+      assert(child.parentData is BlockParentData);
+      child.parentData.position = new Point(0.0, y);
+      y += child.size.height;
+      child = child.parentData.nextSibling;
+    }
+    _childrenHeight = y;
+  }
+
+  void hitTestChildren(HitTestResult result, { Point position }) {
+    defaultHitTestChildren(result, position: position);
+  }
+
+  void paint(PaintingCanvas canvas, Offset offset) {
+    defaultPaint(canvas, offset);
+  }
+
+}
+
+class RenderBlock extends RenderBlockBase {
+
+  // sizes itself to the height of its child stack
+
+  RenderBlock({ List<RenderBox> children }) : super(children: children);
+
   double getMinIntrinsicWidth(BoxConstraints constraints) {
     double width = 0.0;
     BoxConstraints innerConstraints = constraints.widthConstraints();
@@ -77,50 +121,6 @@ abstract class RenderBlockBase extends RenderBox with ContainerRenderObjectMixin
     return _getIntrinsicHeight(constraints);
   }
 
-  double computeDistanceToActualBaseline(TextBaseline baseline) {
-    return defaultComputeDistanceToFirstActualBaseline(baseline);
-  }
-
-  double _childrenHeight;
-  double get childrenHeight => _childrenHeight;
-
-  void markNeedsLayout() {
-    _childrenHeight = null;
-    super.markNeedsLayout();
-  }
-
-  void performLayout() {
-    assert(constraints is BoxConstraints);
-    double width = constraints.constrainWidth(constraints.maxWidth);
-    BoxConstraints innerConstraints = _getInnerConstraintsForWidth(width);
-    double y = 0.0;
-    RenderBox child = firstChild;
-    while (child != null) {
-      child.layout(innerConstraints, parentUsesSize: true);
-      assert(child.parentData is BlockParentData);
-      child.parentData.position = new Point(0.0, y);
-      y += child.size.height;
-      child = child.parentData.nextSibling;
-    }
-    _childrenHeight = y;
-  }
-
-  void hitTestChildren(HitTestResult result, { Point position }) {
-    defaultHitTestChildren(result, position: position);
-  }
-
-  void paint(PaintingCanvas canvas, Offset offset) {
-    defaultPaint(canvas, offset);
-  }
-
-}
-
-class RenderBlock extends RenderBlockBase {
-
-  // sizes itself to the height of its child stack
-
-  RenderBlock({ List<RenderBox> children }) : super(children: children);
-
   bool _hasVisualOverflow = false;
 
   void performLayout() {
@@ -182,6 +182,22 @@ class RenderBlockViewport extends RenderBlockBase {
       markNeedsLayout();
   }
 
+  double getMinIntrinsicWidth(BoxConstraints constraints) {
+    return constraints.constrainWidth();
+  }
+
+  double getMaxIntrinsicWidth(BoxConstraints constraints) {
+    return constraints.constrainWidth();
+  }
+
+  double getMinIntrinsicHeight(BoxConstraints constraints) {
+    return constraints.constrainHeight();
+  }
+
+  double getMaxIntrinsicHeight(BoxConstraints constraints) {
+    return constraints.constrainHeight();
+  }
+
   bool get sizedByParent => true;
 
   void performResize() {