Specs: hit testing (and some cleanup)

sky/examples/style/block-layout.sky

 SKY MODULE
 <import src="sky:core" as="sky"/>
 <!--
  ! this module provides trivial vertical block layout
  ! no margins, padding, borders, etc
  !-->
 <script>
  module.exports.BlockLayoutManager = class BlockLayoutManager extends sky.LayoutManager {
    function layout(width, height) {
      if (width == null)
@@ skipping 19 matching lines @@
      }
      if (autoHeight)
        height = y;
      return {
        width: width,
        height: height,
      }
    }
    function getIntrinsicWidth() {
      let width = this.node.getProperty('width');
-     if (typeof height != 'number') {
+     if (typeof width != 'number') {
        // e.g. width: auto
        width = 0;
        let children = this.walkChildren();
        let loop = children.next();
        while (!loop.done) {
          let child = loop.value;
          let childWidth = child.layoutManager.getIntrinsicWidth();
          if (width < childWidth.value)
            width = childWidth.value;
          loop = children.next();
@@ skipping 14 matching lines @@
          if (height < childHeight.value)
            height = childHeight.value;
          loop = children.next();
        }
      }
      return super(height); // applies and provides our own min-width/max-width rules
    }
  }
  sky.registerLayoutManager('block', module.exports.BlockLayoutManager);
 </script>