Chromad: Add authentication flow

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 7cba697805da512d5819523cd8998bffad5b3de3..0b23559921c6b0a04f299db5c1e4a9ffcb250320 100644
--- a/components/signin/core/account_id/account_id.h
+++ b/components/signin/core/account_id/account_id.h
@@ -18,6 +18,10 @@
 // But in near future AccountId will become full feature user identifier.
 class AccountId {
  public:
+  // Known account types.
+  static const std::string kGoogle;
+  static const std::string kAd;
+
   struct EmptyAccountId;
 
   AccountId(const AccountId& other);
@@ -44,6 +48,7 @@ class AccountId {
 
   void SetGaiaId(const std::string& gaia_id);
   void SetUserEmail(const std::string& email);
+  void SetAccountType(const std::string& account_type);
 
   // This method is to be used during transition period only.
   static AccountId FromUserEmail(const std::string& user_email);
@@ -68,6 +73,7 @@ class AccountId {
 
   std::string gaia_id_;
   std::string user_email_;
+  std::string account_type_ = kGoogle;
 };
 
 // Returns a reference to a singleton.