Translate: Bug fix: Language synonym conversion should preserve a sub code.

For example, if CLD detected the language 'iw' and the lang attribute's value was 'he-IL', they should be recognized as same language codes ('he' and 'iw' mean Hebrew language).

Additionally, this CL fixes LanguageDetectionUtil::IsSameOrSimilarLanguages because this seemed suspicious in the case of three-letter language codes.

BUG=298387
TEST=unit_tests --gtest_filter=TranslateUtilTest.*, unit_tests --gtest_filter=LanguageDetectionUtilTest.*

Review URL: https://codereview.chromium.org/24717002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226227 0039d316-1c4b-4281-b951-d872f2087c98
Revert "Removed the experimental flag for Chromecast support and the corresponding strings."

This reverts commit e3b9d41eaf634d4a60886e50d503d0ad73fc5403.

BUG=299971
NOTRY=true

Review URL: https://codereview.chromium.org/25534002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226228 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 226228