diff --git a/mozilla/layout/html/tests/DumpTree.js b/mozilla/layout/html/tests/DumpTree.js
new file mode 100644
index 00000000000..7dec1e370ee
--- /dev/null
+++ b/mozilla/layout/html/tests/DumpTree.js
@@ -0,0 +1,35 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-*/
+
+function traverse(node, indent)
+{
+  indent += "  ";
+  var type = node.nodeType;
+
+  // if it's an element dump the tag and recurse the children
+  if (type == Node.ELEMENT_NODE) {
+    dump(indent + "<" + node.tagName + ">\n");
+
+    // go through the children
+    if (node.hasChildNodes()) {
+      var children = node.childNodes;
+      var i, length = children.length;
+      for (i = 0; i < length; i++) {
+        var child = children[i];
+        traverse(child, indent);
+      }
+      dump(indent + "</" + node.tagName + ">\n");
+    }
+  }
+  // it's just text, no tag, dump "Text"
+  else if (type == Node.TEXT_NODE) {
+    dump(indent + node.data + "\n");
+  }
+}
+
+function dumpTree()
+{
+  var node = document.documentElement;
+  dump("Document Tree:\n");
+  traverse(node, "");
+  dump("\n");
+}