Clean up child checks in ContainerNode.

sky/tests/resources/dom-utils.sky

Index: sky/tests/resources/dom-utils.sky
diff --git a/sky/tests/resources/dom-utils.sky b/sky/tests/resources/dom-utils.sky
new file mode 100644
index 0000000000000000000000000000000000000000..40668f6c6d40eb66fed2dad1820271100249f557
--- /dev/null
+++ b/sky/tests/resources/dom-utils.sky
@@ -0,0 +1,20 @@
+<script>
+  function childNodeCount(parent) {
+    var count = 0;
+    for (var node = parent.firstChild; node; node = node.nextSibling)
+      ++count;
+    return count;
+  }
+
+  function childElementCount(parent) {
+    var count = 0;
+    for (var element = parent.firstElementChild; element; element = element.nextElementSibling)
+      ++count;
+    return count;
+  }
+
+  module.exports = {
+    childNodeCount: childNodeCount,
+    childElementCount: childElementCount,
+  };
+</script>