diff --git a/gfx/thebes/gfxPlatformFontList.cpp b/gfx/thebes/gfxPlatformFontList.cpp
index 3128b88f75cf..82d82cd077d7 100644
--- a/gfx/thebes/gfxPlatformFontList.cpp
+++ b/gfx/thebes/gfxPlatformFontList.cpp
@@ -2470,131 +2470,8 @@ void gfxPlatformFontList::AppendCJKPrefLangs(eFontPrefLang aPrefLangs[],
     AppendPrefLang(aPrefLangs, aLen, aPageLang);
   }
 
-  // if not set up, set up the default CJK order, based on accept lang
-  // settings and locale
-  if (mCJKPrefLangs.Length() == 0) {
-    // temp array
-    eFontPrefLang tempPrefLangs[kMaxLenPrefLangList];
-    uint32_t tempLen = 0;
-
-    // Add the CJK pref fonts from accept languages, the order should be same
-    // order. We use gfxFontUtils::GetPrefsFontList to read the list even
-    // though it's not actually a list of fonts but of lang codes; the format
-    // is the same.
-    AutoTArray<nsCString, 5> list;
-    gfxFontUtils::GetPrefsFontList("intl.accept_languages", list, true);
-    for (const auto& lang : list) {
-      eFontPrefLang fpl = GetFontPrefLangFor(lang.get());
-      switch (fpl) {
-        case eFontPrefLang_Japanese:
-        case eFontPrefLang_Korean:
-        case eFontPrefLang_ChineseCN:
-        case eFontPrefLang_ChineseHK:
-        case eFontPrefLang_ChineseTW:
-          AppendPrefLang(tempPrefLangs, tempLen, fpl);
-          break;
-        default:
-          break;
-      }
-    }
-
-    // Try using app's locale
-    nsAutoCString localeStr;
-    LocaleService::GetInstance()->GetAppLocaleAsBCP47(localeStr);
-
-    {
-      Locale locale;
-      if (LocaleParser::TryParse(localeStr, locale).isOk() &&
-          locale.Canonicalize().isOk()) {
-        if (locale.Language().EqualTo("ja")) {
-          AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_Japanese);
-        } else if (locale.Language().EqualTo("zh")) {
-          if (locale.Region().EqualTo("CN")) {
-            AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseCN);
-          } else if (locale.Region().EqualTo("TW")) {
-            AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseTW);
-          } else if (locale.Region().EqualTo("HK")) {
-            AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseHK);
-          }
-        } else if (locale.Language().EqualTo("ko")) {
-          AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_Korean);
-        }
-      }
-    }
-
-    // Then add the known CJK prefs in order of system preferred locales
-    AutoTArray<nsCString, 5> prefLocales;
-    prefLocales.AppendElement("ja"_ns);
-    prefLocales.AppendElement("zh-CN"_ns);
-    prefLocales.AppendElement("zh-TW"_ns);
-    prefLocales.AppendElement("zh-HK"_ns);
-    prefLocales.AppendElement("ko"_ns);
-
-    AutoTArray<nsCString, 16> sysLocales;
-    AutoTArray<nsCString, 16> negLocales;
-    if (NS_SUCCEEDED(
-            OSPreferences::GetInstance()->GetSystemLocales(sysLocales))) {
-      LocaleService::GetInstance()->NegotiateLanguages(
-          sysLocales, prefLocales, ""_ns,
-          LocaleService::kLangNegStrategyFiltering, negLocales);
-      for (const auto& localeStr : negLocales) {
-        Locale locale;
-        if (LocaleParser::TryParse(localeStr, locale).isOk() &&
-            locale.Canonicalize().isOk()) {
-          if (locale.Language().EqualTo("ja")) {
-            AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_Japanese);
-          } else if (locale.Language().EqualTo("zh")) {
-            if (locale.Region().EqualTo("CN")) {
-              AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseCN);
-            } else if (locale.Region().EqualTo("TW")) {
-              AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseTW);
-            } else if (locale.Region().EqualTo("HK")) {
-              AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseHK);
-            }
-          } else if (locale.Language().EqualTo("ko")) {
-            AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_Korean);
-          }
-        }
-      }
-    }
-
-    // Last resort... set up CJK font prefs in the order listed by the user-
-    // configurable ordering pref.
-    gfxFontUtils::GetPrefsFontList(kCJKFallbackOrderPref, list);
-    for (const auto& item : list) {
-      eFontPrefLang fpl = GetFontPrefLangFor(item.get());
-      switch (fpl) {
-        case eFontPrefLang_Japanese:
-        case eFontPrefLang_Korean:
-        case eFontPrefLang_ChineseCN:
-        case eFontPrefLang_ChineseHK:
-        case eFontPrefLang_ChineseTW:
-          AppendPrefLang(tempPrefLangs, tempLen, fpl);
-          break;
-        default:
-          break;
-      }
-    }
-
-    // Truly-last resort... try Chinese font prefs before Japanese because
-    // they tend to have more complete character coverage, and therefore less
-    // risk of "ransom-note" effects.
-    // (If the kCJKFallbackOrderPref was fully populated, as it is by default,
-    // this will do nothing as all these values are already present.)
-    AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseCN);
-    AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseHK);
-    AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseTW);
-    AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_Japanese);
-    AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_Korean);
-
-    // copy into the cached array
-    for (const auto lang : Span<eFontPrefLang>(tempPrefLangs, tempLen)) {
-      mCJKPrefLangs.AppendElement(lang);
-    }
-  }
-
   // append in cached CJK langs
-  for (const auto lang : mCJKPrefLangs) {
+  for (const auto lang : GetFontPrefs()->CJKPrefLangs()) {
     AppendPrefLang(aPrefLangs, aLen, eFontPrefLang(lang));
   }
 }
@@ -2934,7 +2811,6 @@ void gfxPlatformFontList::ClearLangGroupPrefFontsLocked() {
       pref = nullptr;
     }
   }
-  mCJKPrefLangs.Clear();
   mEmojiPrefFont = nullptr;
 
   // Create a new FontPrefs and replace the existing one.
@@ -3338,6 +3214,125 @@ void gfxPlatformFontList::FontPrefs::Init() {
     }
   }
   mEmojiHasUserValue = Preferences::HasUserValue("font.name-list.emoji");
+
+  // Record the default CJK order, based on accept-lang settings and locale.
+  eFontPrefLang tempPrefLangs[kMaxLenPrefLangList];
+  uint32_t tempLen = 0;
+
+  // Add the CJK pref fonts from accept languages, the order should be same
+  // order. We use gfxFontUtils::GetPrefsFontList to read the list even
+  // though it's not actually a list of fonts but of lang codes; the format
+  // is the same.
+  AutoTArray<nsCString, 5> list;
+  gfxFontUtils::GetPrefsFontList("intl.accept_languages", list, true);
+  for (const auto& lang : list) {
+    eFontPrefLang fpl = GetFontPrefLangFor(lang.get());
+    switch (fpl) {
+      case eFontPrefLang_Japanese:
+      case eFontPrefLang_Korean:
+      case eFontPrefLang_ChineseCN:
+      case eFontPrefLang_ChineseHK:
+      case eFontPrefLang_ChineseTW:
+        AppendPrefLang(tempPrefLangs, tempLen, fpl);
+        break;
+      default:
+        break;
+    }
+  }
+
+  // Try using app's locale
+  nsAutoCString localeStr;
+  LocaleService::GetInstance()->GetAppLocaleAsBCP47(localeStr);
+
+  {
+    Locale locale;
+    if (LocaleParser::TryParse(localeStr, locale).isOk() &&
+        locale.Canonicalize().isOk()) {
+      if (locale.Language().EqualTo("ja")) {
+        AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_Japanese);
+      } else if (locale.Language().EqualTo("zh")) {
+        if (locale.Region().EqualTo("CN")) {
+          AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseCN);
+        } else if (locale.Region().EqualTo("TW")) {
+          AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseTW);
+        } else if (locale.Region().EqualTo("HK")) {
+          AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseHK);
+        }
+      } else if (locale.Language().EqualTo("ko")) {
+        AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_Korean);
+      }
+    }
+  }
+
+  // Then add the known CJK prefs in order of system preferred locales
+  AutoTArray<nsCString, 5> prefLocales;
+  prefLocales.AppendElement("ja"_ns);
+  prefLocales.AppendElement("zh-CN"_ns);
+  prefLocales.AppendElement("zh-TW"_ns);
+  prefLocales.AppendElement("zh-HK"_ns);
+  prefLocales.AppendElement("ko"_ns);
+
+  AutoTArray<nsCString, 16> sysLocales;
+  AutoTArray<nsCString, 16> negLocales;
+  if (NS_SUCCEEDED(
+          OSPreferences::GetInstance()->GetSystemLocales(sysLocales))) {
+    LocaleService::GetInstance()->NegotiateLanguages(
+        sysLocales, prefLocales, ""_ns,
+        LocaleService::kLangNegStrategyFiltering, negLocales);
+    for (const auto& localeStr : negLocales) {
+      Locale locale;
+      if (LocaleParser::TryParse(localeStr, locale).isOk() &&
+          locale.Canonicalize().isOk()) {
+        if (locale.Language().EqualTo("ja")) {
+          AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_Japanese);
+        } else if (locale.Language().EqualTo("zh")) {
+          if (locale.Region().EqualTo("CN")) {
+            AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseCN);
+          } else if (locale.Region().EqualTo("TW")) {
+            AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseTW);
+          } else if (locale.Region().EqualTo("HK")) {
+            AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseHK);
+          }
+        } else if (locale.Language().EqualTo("ko")) {
+          AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_Korean);
+        }
+      }
+    }
+  }
+
+  // Last resort... set up CJK font prefs in the order listed by the user-
+  // configurable ordering pref.
+  gfxFontUtils::GetPrefsFontList(kCJKFallbackOrderPref, list);
+  for (const auto& item : list) {
+    eFontPrefLang fpl = GetFontPrefLangFor(item.get());
+    switch (fpl) {
+      case eFontPrefLang_Japanese:
+      case eFontPrefLang_Korean:
+      case eFontPrefLang_ChineseCN:
+      case eFontPrefLang_ChineseHK:
+      case eFontPrefLang_ChineseTW:
+        AppendPrefLang(tempPrefLangs, tempLen, fpl);
+        break;
+      default:
+        break;
+    }
+  }
+
+  // Truly-last resort... try Chinese font prefs before Japanese because
+  // they tend to have more complete character coverage, and therefore less
+  // risk of "ransom-note" effects.
+  // (If the kCJKFallbackOrderPref was fully populated, as it is by default,
+  // this will do nothing as all these values are already present.)
+  AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseCN);
+  AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseHK);
+  AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseTW);
+  AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_Japanese);
+  AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_Korean);
+
+  // copy into the cached array
+  for (const auto lang : Span<eFontPrefLang>(tempPrefLangs, tempLen)) {
+    mCJKPrefLangs.AppendElement(lang);
+  }
 }
 
 bool gfxPlatformFontList::FontPrefs::LookupName(const nsACString& aPref,
diff --git a/gfx/thebes/gfxPlatformFontList.h b/gfx/thebes/gfxPlatformFontList.h
index 51d6530e44c0..8b5a09b6b957 100644
--- a/gfx/thebes/gfxPlatformFontList.h
+++ b/gfx/thebes/gfxPlatformFontList.h
@@ -198,6 +198,8 @@ class gfxPlatformFontList : public gfxFontInfoLoader {
       return mFontNameList.ConstIter();
     }
 
+    const nsTArray<uint32_t>& CJKPrefLangs() const { return mCJKPrefLangs; }
+
    private:
     static constexpr char kNamePrefix[] = "font.name.";
     static constexpr char kNameListPrefix[] = "font.name-list.";
@@ -206,6 +208,7 @@ class gfxPlatformFontList : public gfxFontInfoLoader {
 
     HashMap mFontName;
     HashMap mFontNameList;
+    nsTArray<uint32_t> mCJKPrefLangs;
     bool mEmojiHasUserValue = false;
   };
 
@@ -1055,7 +1058,6 @@ class gfxPlatformFontList : public gfxFontInfoLoader {
 
   nsLanguageAtomService* mLangService = nullptr;
 
-  nsTArray<uint32_t> mCJKPrefLangs MOZ_GUARDED_BY(mLock);
   nsTArray<mozilla::StyleGenericFontFamily> mDefaultGenericsLangGroup
       MOZ_GUARDED_BY(mLock);