servo: Merge #14771 - Add support of text-combine-upright for stylo (from upsuper:text-combine-upright); r=Wafflespeanut

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

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- [ ] There are tests for these changes OR
- [x] These changes do not require tests because it is just a trivial change for stylo only

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Source-Repo: https://github.com/servo/servo
Source-Revision: 49bdef98bff28771b189073f5f0d487fe9529b86

servo/components/style/properties/longhand/inherited_text.mako.rs

@@ -1058,3 +1058,11 @@ ${helpers.single_keyword("ruby-align", "start center space-between space-around"
 
 ${helpers.single_keyword("ruby-position", "over under",
                          products="gecko", animatable=False)}
+
+// CSS Writing Modes Module Level 3
+// https://drafts.csswg.org/css-writing-modes-3/#text-combine-upright
+// The spec has "digits <integer>?" value in addition. But that value is
+// at-risk, and Gecko's layout code doesn't support that either. So we
+// can just take the easy way for now.
+${helpers.single_keyword("text-combine-upright", "none all",
+                         products="gecko", animatable=False)}