layout: Add line height from preserved segment breaks in quirks mode (#31419)

In quirks mode, preserved segment breaks should add line height to
lines. This matches the behavior of WebKit and Blink, but not Gecko.

This also handles the special-case of `<br>` elements, which are
implemented with preserved segment breaks via `white-space: pre-line`.
This is an implementation detail though because `<br>` has a special
behavior if the line isn't empty -- it doesn't add any line height in
this case.

components/script/layout_dom/element.rs

@@ -747,6 +747,10 @@ impl<'dom, LayoutDataType: LayoutDataTrait> ThreadSafeLayoutElement<'dom>
         self.element
     }
 
+    fn get_local_name(&self) -> &LocalName {
+        self.element.local_name()
+    }
+
     fn get_attr_enum(&self, namespace: &Namespace, name: &LocalName) -> Option<&AttrValue> {
         self.element.get_attr_enum(namespace, name)
     }