Add test.

servo · Hoverbear · Nov 15, 2014 · Nov 15, 2014 · Nov 15, 2014 · d4f4018e881dd26f503434a65b50994e505b7342
commit d4f4018e881dd26f503434a65b50994e505b7342
diff --git a/tests/content/test_caption.html b/tests/content/test_caption.html
@@ -17,5 +17,8 @@
   t.caption = newCaption;
   is(newCaption.parentNode, t);
   is(t.caption, newCaption);
+
+  // Test for https://github.com/servo/servo/issues/3997
+  t.getBoundingClientRect();
 </script>
 </html>