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

Review URL: https://codereview.chromium.org/163793004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251213 0039d316-1c4b-4281-b951-d872f2087c98

build/common.gypi

@@ -1332,8 +1332,10 @@
             # can use breakpad for these builds.
             'release_unwind_tables%': 0,
           }],
-          # TODO(jungshik): Turn this on on Android and Chrome OS
-          ['OS!="android" and chromeos==0', {
+          # TODO(jungshik): Turn this on on Android.
+          # For ChromeOS, this should be turned on in chromeos-chrome.ebuild
+          # file as well by adding icu_use_data_file_flag=1 to BUILD_DEFINES.
+          ['OS!="android"', {
             'icu_use_data_file_flag%': 1,
           }],
         ],