ChromeOS user_manager: move all KnownUser code to separate file.

chrome/browser/chromeos/login/existing_user_controller.cc

Index: chrome/browser/chromeos/login/existing_user_controller.cc
diff --git a/chrome/browser/chromeos/login/existing_user_controller.cc b/chrome/browser/chromeos/login/existing_user_controller.cc
index 8655f71b6af7e6c6fc1c7ee68bceb5dbc03d170c..bf582228d0572245bebf5da1d7fcea76c0859879 100644
--- a/chrome/browser/chromeos/login/existing_user_controller.cc
+++ b/chrome/browser/chromeos/login/existing_user_controller.cc
@@ -63,6 +63,7 @@
 #include "components/policy/core/common/policy_types.h"
 #include "components/signin/core/account_id/account_id.h"
 #include "components/signin/core/browser/signin_client.h"
+#include "components/user_manager/known_user.h"
 #include "components/user_manager/user_manager.h"
 #include "components/user_manager/user_type.h"
 #include "content/public/browser/browser_thread.h"
@@ -1064,9 +1065,8 @@ void ExistingUserController::ContinueLoginIfDeviceNotDisabled(
 void ExistingUserController::DoCompleteLogin(
     const UserContext& user_context_wo_device_id) {
   UserContext user_context = user_context_wo_device_id;
-  std::string device_id =
-      user_manager::UserManager::Get()->GetKnownUserDeviceId(
-          user_context.GetAccountId());
+  std::string device_id = user_manager::known_user::GetKnownUserDeviceId(
+      user_context.GetAccountId());
   if (device_id.empty()) {
     bool is_ephemeral = ChromeUserManager::Get()->AreEphemeralUsersEnabled() &&
                         user_context.GetAccountId() !=
@@ -1077,7 +1077,7 @@ void ExistingUserController::DoCompleteLogin(
 
   const std::string& gaps_cookie = user_context.GetGAPSCookie();
   if (!gaps_cookie.empty()) {
-    user_manager::UserManager::Get()->SetKnownUserGAPSCookie(
+    user_manager::known_user::SetKnownUserGAPSCookie(
         user_context.GetAccountId(), gaps_cookie);
   }