Auto merge of #15692 - servo:moz-table-border-nonzero, r=upsuper

Stylo: add :-moz-table-border-nonzero pseudo-class.

<!-- Please describe your changes on the following line: -->

https://bugzilla.mozilla.org/show_bug.cgi?id=1340696

---
<!-- 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
- [ ] These changes fix #__ (github issue number if applicable).

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

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

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/15692)
<!-- Reviewable:end -->

components/style/gecko/non_ts_pseudo_class_list.rs

@@ -46,4 +46,5 @@ pseudo_class_list! {
     ("read-only", ReadOnly, _, IN_READ_WRITE_STATE, _),
 
     ("-moz-browser-frame", MozBrowserFrame, mozBrowserFrame, _, PSEUDO_CLASS_INTERNAL),
+    ("-moz-table-border-nonzero", MozTableBorderNonzero, mozTableBorderNonzero, _, PSEUDO_CLASS_INTERNAL),
 }

components/style/gecko/wrapper.rs

@@ -621,6 +621,7 @@ impl<'le> ::selectors::Element for GeckoElement<'le> {
                 !self.get_state().contains(pseudo_class.state_flag())
             }
 
+            NonTSPseudoClass::MozTableBorderNonzero |
             NonTSPseudoClass::MozBrowserFrame => unsafe {
                 Gecko_MatchesElement(pseudo_class.to_gecko_pseudoclasstype().unwrap(), self.0)
             }