Override Date.prototype.to*String with Intl.DateTimeFormat.format

Override Date.prototype.to*String with Intl.DateTimeFormat.format

This CL does two things. 

1. By using Intl.DateTimeFormat, the timezone history is properly
taken into account when formatting date-time in the past or future
when the zone offset is different from the current zone offset.
(e.g. Europe/Moscow)


2. Reset the timezone in cached DateTimeFormat object to the current one unconditionally. This is a bit inefficient. It has to check DateCacheVersion and reset TZ only when necessary. 


BUG=v8:3547, chromium:417640, v8:5022
TEST=See the bug

[jungshik at Google, 2016-05-19 18:32:04]

Description was changed from

==========
Override Date.prototype.to*String with Intl.DateTimeFormat.format

By using Intl.DateTimeFormat, the timezone history is properly
taken into account when formatting date-time in the past or future
when the zone offset is different from the current zone offset.
(e.g. Europe/Moscow)

BUG=v8:3547,chromium:417640
TEST=See the bug
==========

to

==========
Override Date.prototype.to*String with Intl.DateTimeFormat.format

This CL does two things. 

1. By using Intl.DateTimeFormat, the timezone history is properly
taken into account when formatting date-time in the past or future
when the zone offset is different from the current zone offset.
(e.g. Europe/Moscow)


2. Reset the timezone in cached DateTimeFormat object to the current one
unconditionally. This is a bit inefficient. It has to check DateCacheVersion and
reset TZ only when necessary. 


BUG=v8:3547,chromium:417640,v8:5022 
TEST=See the bug
==========

[Dan Ehrenberg, 2017-01-06 03:40:33]

littledan@chromium.org changed reviewers:
+ littledan@chromium.org

[Dan Ehrenberg, 2017-01-06 03:40:33]

Great, this patch is much simpler than I thought it would be.

Is there any sort of option that we might be able to pass into ICU to get all
the time zones printed as GMT[+-]x00 (TLA) as previously?

[Dan Ehrenberg, 2017-02-08 19:34:16]

On 2017/01/06 03:40:33, Dan Ehrenberg wrote:
> Great, this patch is much simpler than I thought it would be.
> 
> Is there any sort of option that we might be able to pass into ICU to get all
> the time zones printed as GMT[+-]x00 (TLA) as previously?

Thanks for following up upstream with the ECMA 402 feature request for more
options to get the right toString behavior
(https://github.com/tc39/ecma402/issues/108), as well as what our behavior
should be for historical timezone data changes
(https://github.com/tc39/ecma262/issues/725). This is all really great work.

Actually, now that I look at it a little more closely, (you probably already
knew this, but) it seems like there are a bunch of places where historical
timezone data would come up, for example, all of the date component getters and
setters (e.g., Date.prototype.getHour()). Monkey-patching from i18n.js is
probably not the right approach if these are affected, since we'd really want to
fix all of them.