servo: Merge #12757 - stylo: Stop restyling display: none elements, remove the has_changed hack that made us use ReconstructFrame unconditionally (from emilio:stylo); r=bholley,pcwalton

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- [x] `./mach build -d` does not report any errors
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r? @bholley

Source-Repo: https://github.com/servo/servo
Source-Revision: 1b2450339c40dbcb65e94a346ea434d45f0edf90

servo/components/layout/construct.rs

@@ -1374,12 +1374,20 @@ impl<'a, ConcreteThreadSafeLayoutNode: ThreadSafeLayoutNode>
         // We visit the kids first and reset their HAS_NEWLY_CONSTRUCTED_FLOW flags after checking
         // them.  NOTE: Make sure not to bail out early before resetting all the flags!
         let mut need_to_reconstruct = false;
+
+        // If the node has display: none, it's possible that we haven't even
+        // styled the children once, so we need to bailout early here.
+        if node.style(self.style_context()).get_box().clone_display() == display::T::none {
+            return false;
+        }
+
         for kid in node.children() {
             if kid.flags().contains(HAS_NEWLY_CONSTRUCTED_FLOW) {
                 kid.remove_flags(HAS_NEWLY_CONSTRUCTED_FLOW);
                 need_to_reconstruct = true
             }
         }
+
         if need_to_reconstruct {
             return false
         }