Auto merge of #14845 - jdm:restyle-ood, r=emilio

Avoid restyling elements that aren't in a document

- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #14480
- [X] There are tests for these changes

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tests/wpt/mozilla/meta/MANIFEST.json

@@ -6438,6 +6438,18 @@
             "url": "/_mozilla/mozilla/iframe/resize_after_load.html"
           }
         ],
+        "mozilla/restyle-out-of-document.html": [
+          {
+            "path": "mozilla/restyle-out-of-document.html",
+            "references": [
+              [
+                "/_mozilla/mozilla/restyle-out-of-document-ref.html",
+                "=="
+              ]
+            ],
+            "url": "/_mozilla/mozilla/restyle-out-of-document.html"
+          }
+        ],
         "mozilla/scrolling_div_background_borders.html": [
           {
             "path": "mozilla/scrolling_div_background_borders.html",
@@ -21732,6 +21744,18 @@
           "url": "/_mozilla/mozilla/iframe/resize_after_load.html"
         }
       ],
+      "mozilla/restyle-out-of-document.html": [
+        {
+          "path": "mozilla/restyle-out-of-document.html",
+          "references": [
+            [
+              "/_mozilla/mozilla/restyle-out-of-document-ref.html",
+              "=="
+            ]
+          ],
+          "url": "/_mozilla/mozilla/restyle-out-of-document.html"
+        }
+      ],
       "mozilla/scrolling_div_background_borders.html": [
         {
           "path": "mozilla/scrolling_div_background_borders.html",