Allow ICU to normalize time zones

src/js/i18n.js

Index: src/js/i18n.js
diff --git a/src/js/i18n.js b/src/js/i18n.js
index b2eef6f18dd126e82fa2df91ffecad55cafacb42..a859a9fbeb9f1028e0c6245364a800651d8e7f29 100644
--- a/src/js/i18n.js
+++ b/src/js/i18n.js
@@ -1574,7 +1574,7 @@ function initializeDateTimeFormat(dateFormat, locales, options) {
   var formatter = %CreateDateTimeFormat(
     requestedLocale, {skeleton: ldmlString, timeZone: tz}, resolved);
 
-  if (!IS_UNDEFINED(tz) && tz !== resolved.timeZone) {

[adamk, 2015/12/10 17:33:13]

I'd be curious why the old code was specifically checking for a match. Did you
find anything in archeology?

[Dan Ehrenberg, 2015/12/10 17:55:36]

Not sure; it's been there since Jochen's snapshot. I was assuming it's because
this is a way of checking which works 99% of the time and makes intuitive sense
(why should it change, anyway? you'd think).

[adamk, 2015/12/10 19:34:07]

Given the lack of any test coverage for this if statement previously, I guess
the best we can do is give this a try.

+  if (resolved.timeZone === "Etc/Unknown") {
     throw MakeRangeError(kUnsupportedTimeZone, tz);
   }