Groom user manager's code.

components/user_manager/user_manager_base.cc

Index: components/user_manager/user_manager_base.cc
diff --git a/components/user_manager/user_manager_base.cc b/components/user_manager/user_manager_base.cc
index abd329c43327cf3e21c76f98af9de767c9d827e8..1ca442bae091c1b320f6e8c7a2cb1e840e44f3ce 100644
--- a/components/user_manager/user_manager_base.cc
+++ b/components/user_manager/user_manager_base.cc
@@ -795,7 +795,7 @@ const User* UserManagerBase::FindUserInList(const std::string& user_id) const {
   return NULL;
 }
 
-const bool UserManagerBase::UserExistsInList(const std::string& user_id) const {
+bool UserManagerBase::UserExistsInList(const std::string& user_id) const {
   const base::ListValue* user_list = GetLocalState()->GetList(kRegularUsers);
   for (size_t i = 0; i < user_list->GetSize(); ++i) {
     std::string email;