Trying to re-land http://codereview.chromium.org/6901141.

src/extensions/experimental/i18n.js

 // Copyright 2006-2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
 //       with the distribution.
 //     * Neither the name of Google Inc. nor the names of its
 //       contributors may be used to endorse or promote products derived
 //       from this software without specific prior written permission.
 //
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-// TODO(cira): Remove v8 prefix from v8Locale once we have stable API.
-v8Locale = function(optLocale) {
+// TODO(cira): Rename v8Locale into LocaleInfo once we have stable API.
+/**
+ * LocaleInfo class is an aggregate class of all i18n API calls.
+ * @param {Object} settings - localeID and regionID to create LocaleInfo from.
+ *   {Array.<string>|string} settings.localeID -
+ *     Unicode identifier of the locale.
+ *     See http://unicode.org/reports/tr35/#BCP_47_Conformance
+ *   {string} settings.regionID - ISO3166 region ID with addition of
+ *     invalid, undefined and reserved region codes.
+ * @constructor
+ */
+v8Locale = function(settings) {
   native function NativeJSLocale();
-  var properties = NativeJSLocale(optLocale);
-  this.locale = properties.locale;
-  this.language = properties.language;
-  this.script = properties.script;
-  this.region = properties.region;
+
+  // Assume user wanted to do v8Locale("sr");
+  if (typeof(settings) === "string") {
+    settings = {'localeID': settings};
+  }
+
+  var properties = NativeJSLocale(
+      v8Locale.createSettingsOrDefault_(settings, {'localeID': 'root'}));
+
+  // Keep the resolved ICU locale ID around to avoid resolving localeID to
+  // ICU locale ID every time BreakIterator, Collator and so forth are called.
+  this.__icuLocaleID__ = properties.icuLocaleID;
+  this.options = {'localeID': properties.localeID,
+                  'regionID': properties.regionID};
 };
 
-v8Locale.availableLocales = function() {
-  native function NativeJSAvailableLocales();
-  return NativeJSAvailableLocales();
+/**
+ * Clones existing locale with possible overrides for some of the options.
+ * @param {!Object} settings - overrides for current locale settings.
+ * @returns {Object} - new LocaleInfo object.
+ */
+v8Locale.prototype.derive = function(settings) {
+  return new v8Locale(
+      v8Locale.createSettingsOrDefault_(settings, this.options));
 };
 
-v8Locale.prototype.maximizedLocale = function() {
-  native function NativeJSMaximizedLocale();
-  return new v8Locale(NativeJSMaximizedLocale(this.locale));
-};
-
-v8Locale.prototype.minimizedLocale = function() {
-  native function NativeJSMinimizedLocale();
-  return new v8Locale(NativeJSMinimizedLocale(this.locale));
-};
-
-v8Locale.prototype.displayLocale_ = function(displayLocale) {
-  var result = this.locale;
-  if (displayLocale !== undefined) {
-    result = displayLocale.locale;
-  }
-  return result;
-};
-
-v8Locale.prototype.displayLanguage = function(optDisplayLocale) {
-  var displayLocale = this.displayLocale_(optDisplayLocale);
-  native function NativeJSDisplayLanguage();
-  return NativeJSDisplayLanguage(this.locale, displayLocale);
-};
-
-v8Locale.prototype.displayScript = function(optDisplayLocale) {
-  var displayLocale = this.displayLocale_(optDisplayLocale);
-  native function NativeJSDisplayScript();
-  return NativeJSDisplayScript(this.locale, displayLocale);
-};
-
-v8Locale.prototype.displayRegion = function(optDisplayLocale) {
-  var displayLocale = this.displayLocale_(optDisplayLocale);
-  native function NativeJSDisplayRegion();
-  return NativeJSDisplayRegion(this.locale, displayLocale);
-};
-
-v8Locale.prototype.displayName = function(optDisplayLocale) {
-  var displayLocale = this.displayLocale_(optDisplayLocale);
-  native function NativeJSDisplayName();
-  return NativeJSDisplayName(this.locale, displayLocale);
-};
-
+/**
+ * v8BreakIterator class implements locale aware segmenatation.
+ * It is not part of EcmaScript proposal.
+ * @param {Object} locale - locale object to pass to break
+ *   iterator implementation.
+ * @param {string} type - type of segmenatation:
+ *   - character
+ *   - word
+ *   - sentence
+ *   - line
+ * @constructor
+ */
 v8Locale.v8BreakIterator = function(locale, type) {
   native function NativeJSBreakIterator();
-  var iterator = NativeJSBreakIterator(locale, type);
+
+  locale = v8Locale.createLocaleOrDefault_(locale);
+  // BCP47 ID would work in this case, but we use ICU locale for consistency.
+  var iterator = NativeJSBreakIterator(locale.__icuLocaleID__, type);
   iterator.type = type;
   return iterator;
 };
 
+/**
+ * Type of the break we encountered during previous iteration.
+ * @type{Enum}
+ */
 v8Locale.v8BreakIterator.BreakType = {
   'unknown': -1,
   'none': 0,
   'number': 100,
   'word': 200,
   'kana': 300,
   'ideo': 400
 };
 
+/**
+ * Creates new v8BreakIterator based on current locale.
+ * @param {string} - type of segmentation. See constructor.
+ * @returns {Object} - new v8BreakIterator object.
+ */
 v8Locale.prototype.v8CreateBreakIterator = function(type) {
-  return new v8Locale.v8BreakIterator(this.locale, type);
+  return new v8Locale.v8BreakIterator(this, type);
 };
 
 // TODO(jungshik): Set |collator.options| to actually recognized / resolved
 // values.
-v8Locale.Collator = function(locale, options) {
+/**
+ * Collator class implements locale-aware sort.
+ * @param {Object} locale - locale object to pass to collator implementation.
+ * @param {Object} settings - collation flags:
+ *   - ignoreCase
+ *   - ignoreAccents
+ *   - numeric
+ * @constructor
+ */
+v8Locale.Collator = function(locale, settings) {
   native function NativeJSCollator();
-  var collator = NativeJSCollator(locale,
-      options === undefined ? {} : options);
+
+  locale = v8Locale.createLocaleOrDefault_(locale);
+  var collator = NativeJSCollator(
+      locale.__icuLocaleID__, v8Locale.createSettingsOrDefault_(settings, {}));
   return collator;
 };
 
-v8Locale.prototype.createCollator = function(options) {
-  return new v8Locale.Collator(this.locale, options);
+/**
+ * Creates new Collator based on current locale.
+ * @param {Object} - collation flags. See constructor.
+ * @returns {Object} - new v8BreakIterator object.
+ */
+v8Locale.prototype.createCollator = function(settings) {
+  return new v8Locale.Collator(this, settings);
 };
+
+/**
+ * Merges user settings and defaults.
+ * Settings that are not of object type are rejected.
+ * Actual property values are not validated, but whitespace is trimmed if they
+ * are strings.
+ * @param {!Object} settings - user provided settings.
+ * @param {!Object} defaults - default values for this type of settings.
+ * @returns {Object} - valid settings object.
+ */
+v8Locale.createSettingsOrDefault_ = function(settings, defaults) {
+  if (!settings || typeof(settings) !== 'object' ) {
+    return defaults;
+  }
+  for (var key in defaults) {
+    if (!settings.hasOwnProperty(key)) {
+      settings[key] = defaults[key];
+    }
+  }
+  // Clean up values, like trimming whitespace.
+  for (var key in settings) {
+    if (typeof(settings[key]) === "string") {
+      settings[key] = settings[key].trim();
+    }
+  }
+
+  return settings;
+};
+
+/**
+ * If locale is valid (defined and of v8Locale type) we return it. If not
+ * we create default locale and return it.
+ * @param {!Object} locale - user provided locale.
+ * @returns {Object} - v8Locale object.
+ */
+v8Locale.createLocaleOrDefault_ = function(locale) {
+  if (!locale || !(locale instanceof v8Locale)) {
+    return new v8Locale();
+  } else {
+    return locale;
+  }
+};