Auto merge of #14989 - notriddle:ellipsis_reflow, r=emilio

Fix the incrmental reflow behavior of text-overflow

This patch allows Servo to incrementally reflow truncated fragments correctly.

* The untruncated version of a fragment is preserved, and when incrementally reflowing, the untruncated version is what gets reflowed. If it needs truncated, it will get truncated again.
* The ellipsis fragments are skipped when incrementally reflowing a line. If it is still needed, it will be recreated.

---

- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #14952
- [X] There are tests for these changes OR

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tests/wpt/mozilla/meta/MANIFEST.json

@@ -5544,6 +5544,18 @@
             "url": "/_mozilla/css/text_overflow_ellipsis.html"
           }
         ],
+        "css/text_overflow_reflow.html": [
+          {
+            "path": "css/text_overflow_reflow.html",
+            "references": [
+              [
+                "/_mozilla/css/text_overflow_reflow_ref.html",
+                "=="
+              ]
+            ],
+            "url": "/_mozilla/css/text_overflow_reflow.html"
+          }
+        ],
         "css/text_overflow_string.html": [
           {
             "path": "css/text_overflow_string.html",
@@ -20880,6 +20892,18 @@
           "url": "/_mozilla/css/text_overflow_ellipsis.html"
         }
       ],
+      "css/text_overflow_reflow.html": [
+        {
+          "path": "css/text_overflow_reflow.html",
+          "references": [
+            [
+              "/_mozilla/css/text_overflow_reflow_ref.html",
+              "=="
+            ]
+          ],
+          "url": "/_mozilla/css/text_overflow_reflow.html"
+        }
+      ],
       "css/text_overflow_string.html": [
         {
           "path": "css/text_overflow_string.html",