Add a mojo interface for AccountId

components/signin/core/account_id/account_id.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_SIGNIN_CORE_ACCOUNT_ID_ACCOUNT_ID_H_
 #define COMPONENTS_SIGNIN_CORE_ACCOUNT_ID_ACCOUNT_ID_H_
 
 #include <stddef.h>
 
 #include <string>
 #include "base/containers/hash_tables.h"
 
 enum class AccountType { UNKNOWN, GOOGLE, ACTIVE_DIRECTORY };
 
 // Type that contains enough information to identify user.
 //
 // TODO(alemate): we are in the process of moving away from std::string as a
 // type for storing user identifier to AccountId. At this time GaiaId is mostly
 // empty, so this type is used as a replacement for e-mail string.
 // But in near future AccountId will become full feature user identifier.
 // TODO(alemate): Rename functions and fields to reflect different types of
 // accounts. (see crbug.com/672253)
 class AccountId {
  public:
   struct EmptyAccountId;
 
+  // Creates an empty account id.
+  //
+  // Note: This constructor is public as it is required for mojo serialization
+  // To create an AccountId object, prefer using the static FromXXXX methods or
+  // the EmptyAccountId method when creating an empty account id.
+  AccountId();
+
   AccountId(const AccountId& other);
 
   // If any of the comparable AccountIds has AccountType == UNKNOWN then it
   // compares emails.
   // If both are not UNKNOWN and not equal then it returns false.
   // If AccountType == GOOGLE then it checks if either ids or emails are equal.
   // If AccountType == ACTIVE_DIRECTORY then it checks if ids and emails are
   // equal.
   bool operator==(const AccountId& other) const;
   bool operator!=(const AccountId& other) const;
@@ skipping 46 matching lines @@
 
   // 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);
 
  private:
-  AccountId();
   AccountId(const std::string& id,
             const std::string& user_email,
             const AccountType& account_type);
 
   std::string id_;
   std::string user_email_;
   AccountType account_type_ = AccountType::UNKNOWN;
 };
 
 // Returns a reference to a singleton.
 const AccountId& EmptyAccountId();
 
 namespace BASE_HASH_NAMESPACE {
 
 // Implement hashing of AccountId, so it can be used as a key in STL containers.
 template <>
 struct hash<AccountId> {
   std::size_t operator()(const AccountId& user_id) const;
 };
 
 }  // namespace BASE_HASH_NAMESPACE
 
 #endif  // COMPONENTS_SIGNIN_CORE_ACCOUNT_ID_ACCOUNT_ID_H_