Bug 1379910 - Add Preference option to change the locale strategy for regional preferences r=fluent-reviewers,jaws,flod

Differential Revision: https://phabricator.services.mozilla.com/D69715

--HG--
extra : moz-landing-system : lando

browser/app/profile/firefox.js

@@ -757,6 +757,8 @@ pref("browser.download.hide_plugins_without_extensions", true);
   pref("browser.backspace_action", 0);
 #endif
 
+pref("intl.regional_prefs.use_os_locales", false);
+
 // this will automatically enable inline spellchecking (if it is available) for
 // editable elements in HTML
 // 0 = spellcheck nothing
@@ -1203,6 +1205,7 @@ pref("services.sync.prefs.sync.dom.event.contextmenu.enabled", true);
 pref("services.sync.prefs.sync.extensions.update.enabled", true);
 pref("services.sync.prefs.sync.extensions.activeThemeID", true);
 pref("services.sync.prefs.sync.intl.accept_languages", true);
+pref("services.sync.prefs.sync.intl.regional_prefs.use_os_locales", true);
 pref("services.sync.prefs.sync.layout.spellcheckDefault", true);
 pref("services.sync.prefs.sync.media.autoplay.default", true);
 pref("services.sync.prefs.sync.media.eme.enabled", true);

browser/components/preferences/in-content/main.inc.xhtml

@@ -326,6 +326,10 @@
     </hbox>
   </hbox>
 
+  <checkbox id="useSystemLocale" hidden="true" 
+            data-l10n-id="use-system-locale" 
+            preference="intl.regional_prefs.use_os_locales"/>
+
   <hbox id="translationBox" hidden="true">
     <hbox align="center" flex="1">
       <checkbox id="translate" preference="browser.translation.detectLanguage"

browser/components/preferences/in-content/main.js

@@ -147,6 +147,7 @@ Preferences.addAll([
 
   // Languages
   { id: "browser.translation.detectLanguage", type: "bool" },
+  { id: "intl.regional_prefs.use_os_locales", type: "bool" },
 
   // General tab
 
@@ -359,7 +360,7 @@ var gMainPane = {
       this.updatePerformanceSettingsBox({ duringChangeEvent: true });
     });
     this.updatePerformanceSettingsBox({ duringChangeEvent: false });
-
+    this.displayUseSystemLocale();
     let connectionSettingsLink = document.getElementById(
       "connectionSettingsLearnMore"
     );
@@ -1369,6 +1370,29 @@ var gMainPane = {
     gMainPane.hideConfirmLanguageChangeMessageBar();
   },
 
+  displayUseSystemLocale() {
+    let appLocale = Services.locale.appLocaleAsBCP47;
+    let regionalPrefsLocales = Services.locale.regionalPrefsLocales;
+    if (!regionalPrefsLocales.length) {
+      return;
+    }
+    let systemLocale = regionalPrefsLocales[0];
+    let localeDisplayname = Services.intl.getLocaleDisplayNames(undefined, [
+      systemLocale,
+    ]);
+    if (!localeDisplayname.length) {
+      return;
+    }
+    let localeName = localeDisplayname[0];
+    if (appLocale.split("-u-")[0] != systemLocale.split("-u-")[0]) {
+      let checkbox = document.getElementById("useSystemLocale");
+      document.l10n.setAttributes(checkbox, "use-system-locale", {
+        localeName,
+      });
+      checkbox.hidden = false;
+    }
+  },
+
   /**
    * Displays the translation exceptions dialog where specific site and language
    * translation preferences can be set.

browser/locales/en-US/browser/preferences/preferences.ftl

@@ -285,6 +285,11 @@ translate-exceptions =
     .label = Exceptions…
     .accesskey = x
 
+# Variables: 
+#    $localeName (string) - Localized name of the locale to be used.
+use-system-locale = 
+   .label = Use your operating system settings for “{ $localeName }” to format dates, times, numbers, and measurements.
+
 check-user-spelling =
     .label = Check your spelling as you type
     .accesskey = t