Move l10n_util's GetCanonicalLocal() function into base/i18n module.

ui/base/l10n/l10n_util.h

Index: ui/base/l10n/l10n_util.h
diff --git a/ui/base/l10n/l10n_util.h b/ui/base/l10n/l10n_util.h
index e2cb27d5c9c1efbc77315df8353ecf8c91b3e08d..c957c3ea2650908e5327648719ac1454adf3b69a 100644
--- a/ui/base/l10n/l10n_util.h
+++ b/ui/base/l10n/l10n_util.h
@@ -20,10 +20,6 @@
 
 namespace l10n_util {
 
-// The same as base::i18n::GetCanonicalLocale(const char*), but takes
-// std::string as an argument.
-UI_BASE_EXPORT std::string GetCanonicalLocale(const std::string& locale);
-
 // Takes normalized locale as |locale|. Returns language part (before '-').
 UI_BASE_EXPORT std::string GetLanguage(const std::string& locale);