Revert of This CL replaces e-mail with AccountId on user selection screen.

components/signin/core/account_id/account_id.h

Index: components/signin/core/account_id/account_id.h
diff --git a/components/signin/core/account_id/account_id.h b/components/signin/core/account_id/account_id.h
index 9f72030bd0e73378dd1d16d66b445e12402d927a..73be4501db5b0ab107937acced10ee17d478a5e2 100644
--- a/components/signin/core/account_id/account_id.h
+++ b/components/signin/core/account_id/account_id.h
@@ -45,13 +45,8 @@
   static AccountId FromUserEmailGaiaId(const std::string& user_email,
                                        const std::string& gaia_id);
 
-  // These are (for now) unstable and cannot be used to store serialized data to
-  // persistent storage. Only in-memory storage is safe.
-  // Serialize() returns JSON dictionary,
-  // Deserialize() restores AccountId after serialization.
-  std::string Serialize() const;
-  static bool Deserialize(const std::string& serialized,
-                          AccountId* out_account_id);
+  // std::string Serialize() const;
+  // static AccountId Deserialize(const std::string& serialized);
 
  private:
   AccountId();