Fix ICU time zone support on iOS

Fix ICU time zone support on iOS

tzfile.h isn't available on iOS, and the time zone is not set the way it is on OS X, so don't define U_TIMEZONE. Also disables a code path in the non-U_TIMEZONE implmentation that makes a correction that is incorrect on iOS.

Fixes the following upstream ICU bugs:
  http://bugs.icu-project.org/trac/ticket/9051
  http://bugs.icu-project.org/trac/ticket/8661

BUG=None
TEST=None (will be covered by base unit tests once they come online upstream)

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=146527

[stuartmorgan, 2012-07-09 08:46:17]

If you aren't the right reviewer for this, can you point me to who would be?

There's already an upstream ICU bug for part of the iOS issue (failing to build
due to not having tzfile.h), so I've pointed to that bug. It appears that
there's no decision upstream on how to resolve it, so I've done something
locally based on our local platform files.

ToT ICU already has changed the comment around the tdiff change saying that it's
not correct on other platforms and if any of those platforms don't define
U_TIMEZONE it would need to be ifdef'd out. So upstream is aware of the issue,
and the fix just requires an upstream decision about how to do iOS-ifdef'ing.

[jungshik at Google, 2012-07-12 16:52:43]

Yeah, I made that upstream change a couple of weeks ago. Sorry for the delay. 
The patch looks good.

[jungshik at Google, 2012-07-12 16:53:41]

On 2012/07/12 16:52:43, Jungshik Shin wrote:
> Yeah, I made that upstream change a couple of weeks ago. Sorry for the delay. 
> The patch looks good.

Can you just add a reference to the upstream ticket (
http://bugs.icu-project.org/trac/ticket/9051 ) in the description so that we can
know that without going to README.chromium?  Thank you.

[jungshik at Google, 2012-07-12 21:06:59]

LGTM (if it's not clear before).

[stuartmorgan, 2012-07-13 05:50:48]

On 2012/07/12 16:53:41, Jungshik Shin wrote:
> Can you just add a reference to the upstream ticket (
> http://bugs.icu-project.org/trac/ticket/9051 ) in the description so that we
can
> know that without going to README.chromium?  Thank you.

Done; I added both that and 8661, and also added 8661 to the readme. Thanks!

[jungshik at Google, 2012-07-13 17:08:29]

Thanks. LGTM