Turn on icu_case_mapping by default

src/js/i18n.js

Index: src/js/i18n.js
diff --git a/src/js/i18n.js b/src/js/i18n.js
index 18d13db9a2c2f96e88f2c96305486ec7cb933cc9..cab68a0f6db2f08525d83bcbd224f973eea036af 100644
--- a/src/js/i18n.js
+++ b/src/js/i18n.js
@@ -1124,7 +1124,7 @@ AddBoundMethod(GlobalIntlCollator, 'compare', compare, 2, 'collator', false);
  * For example \u00DFP (Eszett+P) becomes SSP.
  */
 function isWellFormedCurrencyCode(currency) {
-  return typeof currency == "string" && currency.length == 3 &&
+  return typeof currency === "string" && currency.length === 3 &&
       IS_NULL(%regexp_internal_match(/[^A-Za-z]/, currency));
 }
 
@@ -2024,13 +2024,13 @@ function LocaleConvertCase(s, locales, isToUpper) {
 
   // StringSplit is slower than this.
   var pos = %StringIndexOf(language, '-', 0);
-  if (pos != -1) {
+  if (pos !== -1) {
     language = %_Call(StringSubstring, language, 0, pos);
   }
 
   var CUSTOM_CASE_LANGUAGES = ['az', 'el', 'lt', 'tr'];
   var langIndex = %ArrayIndexOf(CUSTOM_CASE_LANGUAGES, language, 0);
-  if (langIndex == -1) {
+  if (langIndex === -1) {

[jungshik at Google, 2017/01/10 01:22:45]

I tightened the comparison here just in case although it's not likely to help
with the crash. Nonetheless, it should be a good hygiene, I guess.

     // language-independent case conversion.
     return isToUpper ? %StringToUpperCaseI18N(s) : %StringToLowerCaseI18N(s);
   }