servo: Merge #20479 - style: Add a fast path to each_anonymous_content_child (from emilio:anon-child-bit); r=upsuper

If we know that we don't have anon children it is pointless to go through FFI.

Source-Repo: https://github.com/servo/servo
Source-Revision: 107fd47b93e5e8586ca27293052b9fedc75b88e4

--HG--
extra : subtree_source : https%3A//hg.mozilla.org/projects/converted-servo-linear
extra : subtree_revision : c7cb1f3136acb43480759412d087f2b48c332bb5

servo/components/style/gecko/wrapper.rs

@@ -1121,6 +1121,10 @@ impl<'le> TElement for GeckoElement<'le> {
     where
         F: FnMut(Self),
     {
+        if !self.may_have_anonymous_children() {
+            return;
+        }
+
         let array: *mut structs::nsTArray<*mut nsIContent> =
             unsafe { bindings::Gecko_GetAnonymousContentForElement(self.0) };