ChromeOS: fix user signin by alias.

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 4dcf5212ab23fb3a3d379221e688d1ccff452fe4..87df1e06ef4416e1bcf1fece23fe03cceb7ebe67 100644
--- a/components/user_manager/user_manager_base.cc
+++ b/components/user_manager/user_manager_base.cc
@@ -1145,6 +1145,11 @@ void UserManagerBase::SetKnownUserIntegerPref(const UserID& user_id,
   UpdateKnownUserPrefs(user_id, dict, false);
 }
 
+bool UserManagerBase::GetKnownUserCanonicalEmail(const UserID& user_id,
+                                                 std::string* out_email) {
+  return GetKnownUserStringPref(user_id, kCanonicalEmail, out_email);
+}
+
 void UserManagerBase::UpdateGaiaID(const UserID& user_id,
                                    const std::string& gaia_id) {
   SetKnownUserStringPref(user_id, kGAIAIdKey, gaia_id);