Measure container children without intermediate placement

src/widget/position/scroll.rs

@@ -17,10 +17,7 @@ impl Widget for Scroll {
         let whole = UiRegion::FULL;
         let own = painter.placement();
         let answer_len =
-            match painter.known_len(&self.inner, self.axis, whole, [Some(own.x), Some(own.y)]) {
-                Some(len) => len,
-                None => painter.widget(&self.inner).size().axis(self.axis),
-            };
+            painter.measure_len(&self.inner, self.axis, whole, [Some(own.x), Some(own.y)]);
         let content = answer_len.apply_leftover();
         self.container_len = container_len;
         self.content_len = content.to_px(container_len);