Revert of Revert of Turn on icu_use_data_file_flag on CrOS

Revert of Revert of Turn on icu_use_data_file_flag on CrOS (https://codereview.chromium.org/165593002/)

Reason for revert:
https://chromium-review.googlesource.com/#/c/185937/ just got landed and this CL can go in now. 

Original issue's description:
> Revert of Turn on icu_use_data_file_flag on CrOS (https://codereview.chromium.org/163793004/)
> 
> Reason for revert:
> https://chromium-review.googlesource.com/#/c/185937/ has to go in first. 
> 
> 
> Original issue's description:
> > Turn on icu_use_data_file_flag on CrOS
> > 
> > See also https://chromium-review.googlesource.com/#/c/185937/
> > 
> > The switch has to be turned on in two places (chromeos-chrome.ebuild and
> > build/common.gypi). One or the other can get landed separately, though.
> > 
> > BUG=72633
> > TEST=net_unittests:*IDN* and base_unittests:*String*
> > TBR=mark
> > 
> > Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=251213
> 
> TBR=mark@chromium.org
> NOTREECHECKS=true
> NOTRY=true
> BUG=72633
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=251214

TBR=mark@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=72633
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=251220

[jungshik at Google, 2014-02-14 01:13:57]

Created Revert of Revert of Turn on icu_use_data_file_flag on CrOS

[commit-bot: I haz the power, 2014-02-14 01:14:28]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/jshin@chromium.org/164333003/1

[commit-bot: I haz the power, 2014-02-14 01:19:38]

Change committed as 251220

[Mark Mentovai, 2014-02-14 02:05:17]

LGTM

[jungshik at Google, 2014-02-14 08:50:16]

A revert of this CL has been created in
https://codereview.chromium.org/163173003/ by jshin@chromium.org.

The reason for reverting is: CrOS-side change (chromeos-chrome.ebuild) may not
be used by a buildbot.  

./1_autotest_tests/results-27-experimental_login_OwnershipNotRetaken/login_OwnershipNotRetaken/sysinfo/var/log/ui/ui.LATEST
still has 

[0214/002103:FATAL:content_main_runner.cc(735)] Check failed:
base::i18n::InitializeICU().