This CL fixes the issue with login using alternative e-mails.

components/user_manager/user_manager.h

Index: components/user_manager/user_manager.h
diff --git a/components/user_manager/user_manager.h b/components/user_manager/user_manager.h
index 105125b29c5bf8775cc2263c1c427f579bee5e2c..24b8c9aa7c675ec2906b9efb4103f079d56f4a1c 100644
--- a/components/user_manager/user_manager.h
+++ b/components/user_manager/user_manager.h
@@ -359,6 +359,11 @@ class USER_MANAGER_EXPORT UserManager {
                                        const std::string& path,
                                        const int in_value) = 0;
 
+  // Returns true if user's canonical email was found.
+  // Returns it in |out_email|.
+  virtual bool GetKnownUserCanonicalEmail(const UserID& user_id,
+                                          std::string* out_email) = 0;
+
   // Updates |gaia_id| for user with |user_id|.
   // TODO(antrim): Update this once UserID contains GAIA ID.
   virtual void UpdateGaiaID(const UserID& user_id,