If user profile doesn't contain language setting, default to his Google account settings.

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 7c26b80346714764111bdb1039333808b662eec3..0c4e4724ae059049aa60c82d32dfcec8e92a8100 100644
--- a/ui/base/l10n/l10n_util.h
+++ b/ui/base/l10n/l10n_util.h
@@ -20,6 +20,10 @@
 #endif  // OS_MACOSX
 
 namespace l10n_util {
+// This method translates generic locale name to one of locally defined ones.
+// Returns true if succeeded.
+UI_EXPORT bool CheckAndResolveLocale(const std::string& locale,
+                                     std::string* resolved_locale);
 
 // This method is responsible for determining the locale as defined below. In
 // nearly all cases you shouldn't call this, rather use GetApplicationLocale