Firefox 149 adds CSSNumericValue.to() behind pref (#29248)

FF149 CSSNumericValue.to() beind pref

Author: hamishwillee

api/CSSNumericValue.json

@@ -339,7 +339,14 @@
             "chrome_android": "mirror",
             "edge": "mirror",
             "firefox": {
-              "version_added": false,
+              "version_added": "149",
+              "flags": [
+                {
+                  "type": "preference",
+                  "name": "layout.css.typed-om.enabled",
+                  "value_to_set": "true"
+                }
+              ],
               "impl_url": "https://bugzil.la/1278697"
             },
             "firefox_android": "mirror",