Revert of This CL replaces user_manager::UserID with AccountId.

chrome/browser/chromeos/login/users/user_manager_interface.h

Index: chrome/browser/chromeos/login/users/user_manager_interface.h
diff --git a/chrome/browser/chromeos/login/users/user_manager_interface.h b/chrome/browser/chromeos/login/users/user_manager_interface.h
index c6bf205ae6eabbff1664ad84f0aed74c381e4017..4ca26eb8a517597a358a9c4c7ef675adca79f2e8 100644
--- a/chrome/browser/chromeos/login/users/user_manager_interface.h
+++ b/chrome/browser/chromeos/login/users/user_manager_interface.h
@@ -9,8 +9,6 @@
 #include "components/user_manager/user.h"
 #include "components/user_manager/user_type.h"
 
-class AccountId;
-
 namespace chromeos {
 
 class BootstrapManager;
@@ -19,7 +17,7 @@
 class UserFlow;
 class UserImageManager;
 
-// ChromeOS specific add-ons interface for the UserManager.
+// Chrome specific add-ons interface for the UserManager.
 class UserManagerInterface {
  public:
   UserManagerInterface() {}
@@ -27,28 +25,27 @@
 
   virtual BootstrapManager* GetBootstrapManager() = 0;
   virtual MultiProfileUserController* GetMultiProfileUserController() = 0;
-  virtual UserImageManager* GetUserImageManager(
-      const AccountId& account_id) = 0;
+  virtual UserImageManager* GetUserImageManager(const std::string& user_id) = 0;
   virtual SupervisedUserManager* GetSupervisedUserManager() = 0;
 
-  // Method that allows to set |flow| for user identified by |account_id|.
+  // Method that allows to set |flow| for user identified by |user_id|.
   // Flow should be set before login attempt.
   // Takes ownership of the |flow|, |flow| will be deleted in case of login
   // failure.
-  virtual void SetUserFlow(const AccountId& account_id, UserFlow* flow) = 0;
+  virtual void SetUserFlow(const std::string& user_id, UserFlow* flow) = 0;
 
   // Return user flow for current user. Returns instance of DefaultUserFlow if
   // no flow was defined for current user, or user is not logged in.
   // Returned value should not be cached.
   virtual UserFlow* GetCurrentUserFlow() const = 0;
 
-  // Return user flow for user identified by |account_id|. Returns instance of
+  // Return user flow for user identified by |user_id|. Returns instance of
   // DefaultUserFlow if no flow was defined for user.
   // Returned value should not be cached.
-  virtual UserFlow* GetUserFlow(const AccountId& account_id) const = 0;
+  virtual UserFlow* GetUserFlow(const std::string& user_id) const = 0;
 
-  // Resets user flow for user identified by |account_id|.
-  virtual void ResetUserFlow(const AccountId& account_id) = 0;
+  // Resets user flow for user identified by |user_id|.
+  virtual void ResetUserFlow(const std::string& user_id) = 0;
 
   // Returns list of users allowed for supervised user creation.
   // Returns an empty list in cases when supervised user creation or adding new