Auto merge of #8441 - eefriedman:needs-reflow, r=bholley

Make the needs_reflow method actually work correctly.

The document node is always dirty because layout never clears the bit;
instead, check the dirty bit of the root element.

<!-- Reviewable:start -->
[<img src="https://reviewable.io/review_button.png" height=40 alt="Review on Reviewable"/>](https://reviewable.io/reviews/servo/servo/8441)
<!-- Reviewable:end -->

1 files changed, 10 insertions, 3 deletions

diff --git a/components/script/dom/document.rs b/components/script/dom/document.rs
index 34a7846b543..1fda0761c66 100644
--- a/components/script/dom/document.rs
+++ b/components/script/dom/document.rs
@@ -329,9 +329,16 @@ impl Document {
     }
 
     pub fn needs_reflow(&self) -> bool {
-        self.GetDocumentElement().is_some() &&
-        (self.upcast::<Node>().get_has_dirty_descendants() ||
-         !self.modified_elements.borrow().is_empty())
+        // FIXME: This should check the dirty bit on the document,
+        // not the document element. Needs some layout changes to make
+        // that workable.
+        match self.GetDocumentElement() {
+            Some(root) => {
+                root.upcast::<Node>().get_has_dirty_descendants() ||
+                !self.modified_elements.borrow().is_empty()
+            }
+            None => false,
+        }
     }
 
     /// Returns the first `base` element in the DOM that has an `href` attribute.