ChromeOS user_manager: move all KnownUser code to separate file.

chrome/browser/chromeos/login/screens/chrome_user_selection_screen.cc

Index: chrome/browser/chromeos/login/screens/chrome_user_selection_screen.cc
diff --git a/chrome/browser/chromeos/login/screens/chrome_user_selection_screen.cc b/chrome/browser/chromeos/login/screens/chrome_user_selection_screen.cc
index 4d00564d9d22a01d642ba3a8784aa6d7248ed084..22897dce7893ff5502dcf5018ff1ba623c38448f 100644
--- a/chrome/browser/chromeos/login/screens/chrome_user_selection_screen.cc
+++ b/chrome/browser/chromeos/login/screens/chrome_user_selection_screen.cc
@@ -22,6 +22,7 @@
 #include "components/policy/core/common/policy_map.h"
 #include "components/policy/core/common/policy_types.h"
 #include "components/signin/core/account_id/account_id.h"
+#include "components/user_manager/known_user.h"
 #include "components/user_manager/user.h"
 #include "components/user_manager/user_manager.h"
 #include "components/user_manager/user_type.h"
@@ -77,9 +78,8 @@ void ChromeUserSelectionScreen::OnDeviceLocalAccountsChanged() {
 
 void ChromeUserSelectionScreen::CheckForPublicSessionDisplayNameChange(
     policy::DeviceLocalAccountPolicyBroker* broker) {
-  const AccountId& account_id =
-      user_manager::UserManager::GetKnownUserAccountId(broker->user_id(),
-                                                       std::string());
+  const AccountId& account_id = user_manager::known_user::GetKnownUserAccountId(
+      broker->user_id(), std::string());
   DCHECK(account_id.is_valid());
   const std::string& display_name = broker->GetDisplayName();
   if (display_name == public_session_display_names_[account_id])
@@ -109,9 +109,8 @@ void ChromeUserSelectionScreen::CheckForPublicSessionDisplayNameChange(
 
 void ChromeUserSelectionScreen::CheckForPublicSessionLocalePolicyChange(
     policy::DeviceLocalAccountPolicyBroker* broker) {
-  const AccountId& account_id =
-      user_manager::UserManager::GetKnownUserAccountId(broker->user_id(),
-                                                       std::string());
+  const AccountId& account_id = user_manager::known_user::GetKnownUserAccountId(
+      broker->user_id(), std::string());
   DCHECK(account_id.is_valid());
   const policy::PolicyMap::Entry* entry =
       broker->core()->store()->policy_map().Get(policy::key::kSessionLocales);