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

chrome/browser/chromeos/login/mock_user_manager.cc

Index: chrome/browser/chromeos/login/mock_user_manager.cc
diff --git a/chrome/browser/chromeos/login/mock_user_manager.cc b/chrome/browser/chromeos/login/mock_user_manager.cc
index 43501f570a85ae4be4d0f83f033dcfbc0f85d478..afb462fe0d3a2f41dbb9c4ec68a2f941925c6b53 100644
--- a/chrome/browser/chromeos/login/mock_user_manager.cc
+++ b/chrome/browser/chromeos/login/mock_user_manager.cc
@@ -29,6 +29,10 @@ User* MockUserManager::GetActiveUser() {
   return user_;
 }
 
+const User* MockUserManager::GetPrimaryUser() const {
+  return user_;
+}
+
 UserImageManager* MockUserManager::GetUserImageManager() {
   return user_image_manager_.get();
 }