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 4ca26eb8a517597a358a9c4c7ef675adca79f2e8..8a619ad0cc6c7e7745bd03a3bb83b68d664a2e33 100644
--- a/chrome/browser/chromeos/login/users/user_manager_interface.h
+++ b/chrome/browser/chromeos/login/users/user_manager_interface.h
@@ -9,6 +9,8 @@
 #include "components/user_manager/user.h"
 #include "components/user_manager/user_type.h"
 
+class AccountId;
+
 namespace chromeos {
 
 class BootstrapManager;
@@ -25,14 +27,14 @@ class UserManagerInterface {
 
   virtual BootstrapManager* GetBootstrapManager() = 0;
   virtual MultiProfileUserController* GetMultiProfileUserController() = 0;
-  virtual UserImageManager* GetUserImageManager(const std::string& user_id) = 0;
+  virtual UserImageManager* GetUserImageManager(const AccountId& user_id) = 0;

[achuithb, 2015/10/23 00:08:51]

account_id, here and below

[Alexander Alekseev, 2015/10/23 09:11:23]

Done.

   virtual SupervisedUserManager* GetSupervisedUserManager() = 0;
 
   // 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 std::string& user_id, UserFlow* flow) = 0;
+  virtual void SetUserFlow(const AccountId& 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.
@@ -42,10 +44,10 @@ class UserManagerInterface {
   // 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 std::string& user_id) const = 0;
+  virtual UserFlow* GetUserFlow(const AccountId& user_id) const = 0;
 
   // Resets user flow for user identified by |user_id|.
-  virtual void ResetUserFlow(const std::string& user_id) = 0;
+  virtual void ResetUserFlow(const AccountId& 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