Auto merge of #25627 - pshaughn:definedpseudo, r=emilio,jdm

Implement :defined CSS selector

<!-- Please describe your changes on the following line: -->
ElementState::IN_DEFINED_STATE already existed but wasn't hooked up to anything; now it is set appropriately, and CSS is aware of it. The main test for this selector needed the window named getter for no important reason, so I made a one-line test change to avoid that. Remaining failures in the test are all about SVG elements.

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `___` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #25010

<!-- Either: -->
- [X] There are tests for these changes OR
- [ ] These changes do not require tests because ___

<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

1 files changed, 1 insertions, 0 deletions

diff --git a/components/layout_thread_2020/dom_wrapper.rs b/components/layout_thread_2020/dom_wrapper.rs
index 520014837db..e2bdc0f42a6 100644
--- a/components/layout_thread_2020/dom_wrapper.rs
+++ b/components/layout_thread_2020/dom_wrapper.rs
@@ -962,6 +962,7 @@ impl<'le> ::selectors::Element for ServoLayoutElement<'le> {
             NonTSPseudoClass::Focus |
             NonTSPseudoClass::Fullscreen |
             NonTSPseudoClass::Hover |
+            NonTSPseudoClass::Defined |
             NonTSPseudoClass::Enabled |
             NonTSPseudoClass::Disabled |
             NonTSPseudoClass::Checked |