Async initialization for DateFormat

pkg/intl/data/dates/symbols/zh_CN.json

Index: pkg/intl/data/dates/symbols/zh_CN.json
===================================================================
--- pkg/intl/data/dates/symbols/zh_CN.json	(revision 0)
+++ pkg/intl/data/dates/symbols/zh_CN.json	(revision 0)
@@ -0,0 +1 @@
+{"DATEFORMATS":["y年M月d日EEEE","y年M月d日","yyyy-M-d","yy-M-d"],"NARROWWEEKDAYS":["日","一","二","三","四","五","六"],"STANDALONESHORTMONTHS":["一月","二月","三月","四月","五月","六月","七月","八月","九月","十月","十一月","十二月"],"ERANAMES":["公元前","公元"],"FIRSTWEEKCUTOFFDAY":5,"NARROWMONTHS":["1","2","3","4","5","6","7","8","9","10","11","12"],"STANDALONESHORTWEEKDAYS":["周日","周一","周二","周三","周四","周五","周六"],"FIRSTDAYOFWEEK":6,"STANDALONEWEEKDAYS":["星期日","星期一","星期二","星期三","星期四","星期五","星期六"],"WEEKDAYS":["星期日","星期一","星期二","星期三","星期四","星期五","星期六"],"QUARTERS":["第1季度","第2季度","第3季度","第4季度"],"ERAS":["公元前","公元"],"MONTHS":["1月","2月","3月","4月","5月","6月","7月","8月","9月","10月","11月","12月"],"TIMEFORMATS":["zzzzah时mm分ss秒","zah时mm分ss秒","ah:mm:ss","ah:mm"],"SHORTWEEKDAYS":["周日","周一","周二","周三","周四","周五","周六"],"SHORTQUARTERS":["1季","2季","3季","4季"],"WEEKENDRANGE":[5,6],"STANDALONENARROWWEEKDAYS":["日","一","二","三","四","五","六"],"AVAILABLEFORMATS":null,"NAME":"zh_CN","AMPMS":["上午","下午"],"STANDALONEMONTHS":["一月","二月","三月","四月","五月","六月","七月","八月","九月","十月","十一月","十二月"],"SHORTMONTHS":["1月","2月","3月","4月","5月","6月","7月","8月","9月","10月","11月","12月"],"STANDALONENARROWMONTHS":["1月","2月","3月","4月","5月","6月","7月","8月","9月","10月","11月","12月"]}