Don't perform a microtask checkpoint for document.write('<script><\/script>')

LayoutTests/fast/dom/MutationObserver/script-end-tag.html

Index: LayoutTests/fast/dom/MutationObserver/script-end-tag.html
diff --git a/LayoutTests/fast/dom/MutationObserver/script-end-tag.html b/LayoutTests/fast/dom/MutationObserver/script-end-tag.html
index 76870ad45c9575ebc1fdb8c1a4030c70790bc69b..4f4daacf132782d94c8940c75f0a5c6b2c0174f4 100644
--- a/LayoutTests/fast/dom/MutationObserver/script-end-tag.html
+++ b/LayoutTests/fast/dom/MutationObserver/script-end-tag.html
@@ -12,7 +12,9 @@ var observer = new MutationObserver(callback);
 var div = document.createElement('div');
 observer.observe(div, {attributes: true});
 div.setAttribute('foo', 'bar');
+document.write('<script><\/script>');
 shouldBeFalse('mutationsDelivered');
-document.write('<script><\/script>'); // performs a microtask checkpoint
+</script>
+<script>
 shouldBeTrue('mutationsDelivered');
 </script>