Use BCP47 compliant format for locale representation

base/android/java/src/org/chromium/base/LocaleUtils.java

Index: base/android/java/src/org/chromium/base/LocaleUtils.java
diff --git a/base/android/java/src/org/chromium/base/LocaleUtils.java b/base/android/java/src/org/chromium/base/LocaleUtils.java
index 35d04a9b73b8e337f8469420e4141343810b2ef3..31e5c4294beafcc99f3d48eed1675e93cd7dd720 100644
--- a/base/android/java/src/org/chromium/base/LocaleUtils.java
+++ b/base/android/java/src/org/chromium/base/LocaleUtils.java
@@ -4,9 +4,15 @@
 
 package org.chromium.base;
 
+import android.annotation.TargetApi;
+import android.os.Build;
+
 import org.chromium.base.annotations.CalledByNative;
 
+import java.util.Collections;
+import java.util.HashMap;
 import java.util.Locale;
+import java.util.Map;
 
 /**
  * This class provides the locale related methods.
@@ -18,45 +24,154 @@ public class LocaleUtils {
     private LocaleUtils() {
     }
 
+    private static final Map<String, String> LANGUAGE_MAP_FOR_CHROMIUM;
+    private static final Map<String, String> LANGUAGE_MAP_FOR_ANDROID;
+
+    static {
+        HashMap<String, String> mapForChromium = new HashMap<>();
+        mapForChromium.put("iw", "he"); // Hebrew
+        mapForChromium.put("ji", "yi"); // Yiddish
+        mapForChromium.put("in", "id"); // Indonesian
+        mapForChromium.put("tl", "fil"); // Filipino
+        LANGUAGE_MAP_FOR_CHROMIUM = Collections.unmodifiableMap(mapForChromium);
+    }
+
+    static {
+        HashMap<String, String> mapForAndroid = new HashMap<>();
+        mapForAndroid.put("und", ""); // Undefined
+        mapForAndroid.put("fil", "tl"); // Filipino
+        LANGUAGE_MAP_FOR_ANDROID = Collections.unmodifiableMap(mapForAndroid);
+    }
+
     /**
-     * @return The string for the given locale, translating Android deprecated language codes
-     *         into the modern ones used by Chromium.
+     * Java keeps deprecated language codes for Hebrew, Yiddish and Indonesian but Chromium uses
+     * updated ones. Similarly, Android uses "tl" while Chromium uses "fil" for Tagalog/Filipino.
+     * So apply a mapping here.
+     * See http://developer.android.com/reference/java/util/Locale.html
+     * @return a updated language code for Chromium with given language string.
      */
-    public static String getLocale(Locale locale) {
-        String language = getLanguage(locale);
-        String country = locale.getCountry();
+    public static String getUpdatedLanguageForChromium(String language) {
+        String updatedLanguageCode = LANGUAGE_MAP_FOR_CHROMIUM.get(language);
+        return updatedLanguageCode == null ? language : updatedLanguageCode;
+    }
+
+    /**
+     * @return a locale with updated language codes for Chromium, with translated modern language
+     *         codes used by Chromium.
+     */
+    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
+    private static Locale getUpdatedLocaleForChromium(Locale locale) {
+        String languageForChrome = LANGUAGE_MAP_FOR_CHROMIUM.get(locale.getLanguage());
+        if (languageForChrome == null) {
+            return locale;
+        }
+        return new Locale.Builder().setLocale(locale).setLanguage(languageForChrome).build();
+    }
+
+    /**
+     * Android uses "tl" while Chromium uses "fil" for Tagalog/Filipino.
+     * So apply a mapping here.
+     * See http://developer.android.com/reference/java/util/Locale.html
+     * @return a updated language code for Android with given language string.
+     */
+    public static String getUpdatedLanguageForAndroid(String language) {
+        String updatedLanguageCode = LANGUAGE_MAP_FOR_ANDROID.get(language);
+        return updatedLanguageCode == null ? language : updatedLanguageCode;
+    }
 
+    /**
+     * @return a locale with updated language codes for Android, from translated modern language
+     *         codes used by Chromium.
+     */
+    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
+    private static Locale getUpdatedLocaleForAndroid(Locale locale) {
+        String languageForAndroid = LANGUAGE_MAP_FOR_ANDROID.get(locale.getLanguage());
+        if (languageForAndroid == null) {
+            return locale;
+        }
+        return new Locale.Builder().setLocale(locale).setLanguage(languageForAndroid).build();
+    }
+
+    /**
+     * This function creates Locale object from xx-XX style string where xx is language code
+     * and XX is a country code. This works for API level lower than 21.
+     * @return the locale that best represents the language tag.
+     */
+    public static Locale forLanguageTagCompat(String languageTag) {
+        String[] tag = languageTag.split("-");
+        if (tag.length == 0) {
+            return new Locale("");
+        }
+        String language = getUpdatedLanguageForAndroid(tag[0]);
+        if ((language.length() != 2 && language.length() != 3) || language.equals("und")) {
+            return new Locale("");
+        }
+        if (tag.length == 1) {
+            return new Locale(language);
+        }
+        String country = tag[1];
+        if (country.length() != 2 && country.length() != 3) {
+            return new Locale(language);
+        }
+        return new Locale(language, country);
+    }
+
+    /**
+     * This function creates Locale object from xx-XX style string where xx is language code
+     * and XX is a country code.
+     * @return the locale that best represents the language tag.
+     */
+    public static Locale forLanguageTag(String languageTag) {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
+            Locale locale = Locale.forLanguageTag(languageTag);
+            return getUpdatedLocaleForAndroid(locale);
+        }
+        return forLanguageTagCompat(languageTag);
+    }
+
+    /**
+     * Converts Locale object to the BCP 47 compliant string format.
+     * This works for API level lower than 24.
+     * @return a well-formed IETF BCP 47 language tag with language and country code that
+     *         represents this locale.
+     */
+    public static String toLanguageTagCompat(Locale locale) {
+        String language = getUpdatedLanguageForChromium(locale.getLanguage());
+        String country = locale.getCountry();
+        if (language.equals("no") && country.equals("NO") && locale.getVariant().equals("NY")) {
+            return "nn-NO";
+        }
         return country.isEmpty() ? language : language + "-" + country;
     }
 
     /**
-     * @return The language for the given locale, translating Android deprecated languages codes
-     *         into modern ones used by Chromium.
+     * Converts Locale object to the BCP 47 compliant string format.
+     *
+     * Note that for Android M or before, we cannot use Locale.getLanguage() and
+     * Locale.toLanguageTag() for this purpose. Since Locale.getLanguage() returns deprecated
+     * language code even if the Locale object is constructed with updated language code. As for
+     * Locale.toLanguageTag(), it does a special conversion from deprecated language code to updated
+     * one, but it is only usable for Android N or after.
+     * @return a well-formed IETF BCP 47 language tag with language and country code that
+     *         represents this locale.
      */
-    public static String getLanguage(Locale locale) {
-        String language = locale.getLanguage();
-
-        // Android uses deprecated lanuages codes for Hebrew and Indonesian but Chromium uses the
-        // updated codes. Also, Android uses "tl" while Chromium uses "fil" for Tagalog/Filipino.
-        // So apply a mapping.
-        // See http://developer.android.com/reference/java/util/Locale.html
-        if ("iw".equals(language)) {
-            language = "he";
-        } else if ("in".equals(language)) {
-            language = "id";
-        } else if ("tl".equals(language)) {
-            language = "fil";
+    public static String toLanguageTag(Locale locale) {
+        // TODO(yirui): use '>= N' once SDK is updated to include the version code
+        if (Build.VERSION.SDK_INT > Build.VERSION_CODES.M) {
+            locale = getUpdatedLocaleForChromium(locale);
+            return locale.toLanguageTag();
         }
-        return language;
+        return toLanguageTagCompat(locale);
     }
 
     /**
-     * @return The default locale, translating Android deprecated language codes into the modern
-     *         ones used by Chromium.
+     * @return a well-formed IETF BCP 47 language tag with language and country code that
+     *         represents a default locale.
      */
     @CalledByNative
-    public static String getDefaultLocale() {
-        return getLocale(Locale.getDefault());
+    public static String getDefaultLocaleString() {
+        Locale locale = Locale.getDefault();
+        return toLanguageTag(locale);
     }
 
     /**