Auto merge of #20012 - alexfjw:avoid_Window-GetComputedStyle_when_checking_for_display-none, r=emilio

Avoid `Window::GetComputedStyle` when checking for `display: none`

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Refactored Window::GetComputedStyle to use Element::Style.

Not sure which tests are relevant, but I've ran the dom, fetch & 2dcontext wpt tests. They don't seem to give errors.

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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #19885.

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- [x] These changes do not require tests because it's a refactoring task

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components/script/dom/element.rs

@@ -350,7 +350,7 @@ impl Element {
 
     /// style will be `None` for elements in a `display: none` subtree. otherwise, the element has a
     /// layout box iff it doesn't have `display: none`.
-    fn style(&self) -> Option<Arc<ComputedValues>> {
+    pub fn style(&self) -> Option<Arc<ComputedValues>> {
         window_from_node(self).style_query(
             self.upcast::<Node>().to_trusted_node_address()
         )