Async initialization for DateFormat

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

Index: pkg/intl/data/dates/symbols/ja.json
===================================================================
--- pkg/intl/data/dates/symbols/ja.json	(revision 0)
+++ pkg/intl/data/dates/symbols/ja.json	(revision 0)
@@ -0,0 +1 @@
+{"DATEFORMATS":["y年M月d日EEEE","y年M月d日","yyyy/MM/dd","yyyy/MM/dd"],"NARROWWEEKDAYS":["日","月","火","水","木","金","土"],"STANDALONESHORTMONTHS":["1月","2月","3月","4月","5月","6月","7月","8月","9月","10月","11月","12月"],"ERANAMES":["紀元前","西暦"],"FIRSTWEEKCUTOFFDAY":5,"NARROWMONTHS":["1","2","3","4","5","6","7","8","9","10","11","12"],"STANDALONESHORTWEEKDAYS":["日","月","火","水","木","金","土"],"FIRSTDAYOFWEEK":6,"STANDALONEWEEKDAYS":["日曜日","月曜日","火曜日","水曜日","木曜日","金曜日","土曜日"],"WEEKDAYS":["日曜日","月曜日","火曜日","水曜日","木曜日","金曜日","土曜日"],"QUARTERS":["第1四半期","第2四半期","第3四半期","第4四半期"],"ERAS":["紀元前","西暦"],"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":["H時mm分ss秒 zzzz","H:mm:ss z","H:mm:ss","H:mm"],"SHORTWEEKDAYS":["日","月","火","水","木","金","土"],"SHORTQUARTERS":["Q1","Q2","Q3","Q4"],"WEEKENDRANGE":[5,6],"STANDALONENARROWWEEKDAYS":["日","月","火","水","木","金","土"],"AVAILABLEFORMATS":null,"NAME":"ja","AMPMS":["午前","午後"],"STANDALONEMONTHS":["1月","2月","3月","4月","5月","6月","7月","8月","9月","10月","11月","12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","2","3","4","5","6","7","8","9","10","11","12"]}