Pass the document instead of the documentElement to reflow.

components/layout/wrapper.rs

@@ -43,6 +43,7 @@ use script::dom::bindings::codegen::InheritTypes::{HTMLElementTypeId, NodeTypeId
 use script::dom::bindings::conversions::Castable;
 use script::dom::bindings::js::LayoutJS;
 use script::dom::characterdata::LayoutCharacterDataHelpers;
+use script::dom::document::{Document, LayoutDocumentHelpers};
 use script::dom::element;
 use script::dom::element::{Element, LayoutElementHelpers, RawLayoutElementHelpers};
 use script::dom::htmlcanvaselement::{LayoutHTMLCanvasElementHelpers, HTMLCanvasData};
@@ -105,6 +106,12 @@ impl<'ln> LayoutNode<'ln> {
         }
     }
 
+    pub fn is_element(&self) -> bool {
+        unsafe {
+            self.node.is_element_for_layout()
+        }
+    }
+
     pub fn dump(self) {
         self.dump_indent(0);
     }
@@ -336,6 +343,30 @@ impl<'a> Iterator for LayoutTreeIterator<'a> {
     }
 }
 
+// A wrapper around documents that ensures ayout can only ever access safe properties.
+#[derive(Copy, Clone)]
+pub struct LayoutDocument<'le> {
+    document: LayoutJS<Document>,
+    chain: PhantomData<&'le ()>,
+}
+
+impl<'le> LayoutDocument<'le> {
+    pub fn as_node(&self) -> LayoutNode<'le> {
+        LayoutNode {
+            node: self.document.upcast(),
+            chain: PhantomData,
+        }
+    }
+
+    pub fn root_node(&self) -> Option<LayoutNode<'le>> {
+        let mut node = self.as_node().first_child();
+        while node.is_some() && !node.unwrap().is_element() {
+            node = node.unwrap().next_sibling();
+        }
+        node
+    }
+}
+
 /// A wrapper around elements that ensures layout can only ever access safe properties.
 #[derive(Copy, Clone)]
 pub struct LayoutElement<'le> {