Auto merge of #9317 - MonsieurLanza:DomContentLoadedBubbles, r=KiChjang

DOMContentLoaded should bubble.

DOMContentLoaded event is currently set as non bubbling event.
Test :
./tests/wpt/web-platform-tests/html/syntax/parsing/the-end.html

<!-- Reviewable:start -->
[<img src="https://reviewable.io/review_button.png" height=40 alt="Review on Reviewable"/>](https://reviewable.io/reviews/servo/servo/9317)
<!-- Reviewable:end -->

components/script/dom/document.rs

@@ -1352,7 +1352,7 @@ impl Document {
 
         let event = Event::new(GlobalRef::Window(self.window()),
                                atom!("DOMContentLoaded"),
-                               EventBubbles::DoesNotBubble,
+                               EventBubbles::Bubbles,
                                EventCancelable::NotCancelable);
         let doctarget = self.upcast::<EventTarget>();
         let _ = doctarget.DispatchEvent(event.r());