Auto merge of #16044 - bd339:iss15754, r=emilio

Make writing-mode affect computed display

<!-- Please describe your changes on the following line: -->
The first manual test-case in #15754 passes now, but the second test-case still renders "Text" horizontally, which is apparently because of servo's experimental support for writing-mode.

---
<!-- 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 #15754 (github issue number if applicable).

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

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tests/wpt/mozilla/meta/MANIFEST.json

@@ -11142,6 +11142,12 @@
      {}
     ]
    ],
+   "css/writing-mode_change_display.html": [
+    [
+     "/_mozilla/css/writing-mode_change_display.html",
+     {}
+    ]
+   ],
    "mozilla/DOMParser.html": [
     [
      "/_mozilla/mozilla/DOMParser.html",
@@ -24145,6 +24151,10 @@
    "b16bf3e07cb3c45f7d630ca35bae1012d38d1b6b",
    "support"
   ],
+  "css/writing-mode_change_display.html": [
+   "9ac1f9756a4cd44196242beb80621b9bc8cbe2ff",
+   "testharness"
+  ],
   "mozilla/2x2.png": [
    "c67d3f646e86413722833d2308a9bfc793a916bf",
    "support"

tests/wpt/mozilla/meta/css/writing-mode_change_display.html.ini

@@ -0,0 +1 @@
+prefs: [layout.writing-mode.enabled:true]