Fix Document#elementsFromPoint no viewport available test

components/script/dom/document.rs

@@ -1551,8 +1551,6 @@ impl Document {
     }
 
     pub fn nodes_from_point(&self, page_point: &Point2D<f32>) -> Vec<UntrustedNodeAddress> {
-        assert!(self.GetDocumentElement().is_some());
-
         self.window.layout().nodes_from_point(*page_point)
     }
 }
@@ -2718,6 +2716,10 @@ impl DocumentMethods for Document {
         let window = window_from_node(self);
         let viewport = window.window_size().unwrap().visible_viewport;
 
+        if self.browsing_context().is_none() {
+            return vec!();
+        }
+
         // Step 2
         if x < 0.0 || y < 0.0 || x > viewport.width.get() || y > viewport.height.get() {
             return vec!();

tests/wpt/metadata/cssom-view/elementsFromPoint.html.ini

@@ -12,6 +12,3 @@
   [no hit target at x,y]
     expected: FAIL
 
-  [No viewport available]
-    expected: FAIL
-