Adding mojo calls for easy unlock service

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

Index: chrome/browser/chromeos/login/screens/user_selection_screen.cc
diff --git a/chrome/browser/chromeos/login/screens/user_selection_screen.cc b/chrome/browser/chromeos/login/screens/user_selection_screen.cc
index 7678705dbb03c1847712689540dfccb20e72c551..e773b70cfff2042be3abd3dda1c1b7faee9cc152 100644
--- a/chrome/browser/chromeos/login/screens/user_selection_screen.cc
+++ b/chrome/browser/chromeos/login/screens/user_selection_screen.cc
@@ -28,6 +28,7 @@
 #include "chrome/browser/chromeos/policy/browser_policy_connector_chromeos.h"
 #include "chrome/browser/chromeos/profiles/profile_helper.h"
 #include "chrome/browser/signin/easy_unlock_service.h"
+#include "chrome/browser/ui/ash/lock_screen_client.h"
 #include "chrome/browser/ui/webui/chromeos/login/l10n_util.h"
 #include "chrome/browser/ui/webui/chromeos/login/signin_screen_handler.h"
 #include "chrome/grit/generated_resources.h"
@@ -540,7 +541,12 @@ void UserSelectionScreen::SendUserList() {
     users_list.Append(std::move(user_dict));
   }
 
-  handler_->LoadUsers(users_list, show_guest_);
+  if (handler_) {
+    handler_->LoadUsers(users_list, show_guest_);
+  } else {
+    // Views-based lock screen won't instantiate handler.
+    LockScreenClient::Get()->LoadUsers(users_list, show_guest_);

[jdufault, 2017/05/31 22:54:00]

FYI, https://codereview.chromium.org/2811383002/. Might make the mojom interface
a bit simpler since it won't be proxying through a dict.

[xiaoyinh(OOO Sep 11-29), 2017/06/02 23:42:29]

Thanks for the information.

+  }
 }
 
 void UserSelectionScreen::HandleGetUsers() {
@@ -656,7 +662,9 @@ void UserSelectionScreen::AttemptEasySignin(const AccountId& account_id,
   user_context.SetKey(Key(secret));
   user_context.GetKey()->SetLabel(key_label);
 
-  login_display_delegate_->Login(user_context, SigninSpecifics());
+  // login display delegate not exist in views-based lock screen.
+  if (login_display_delegate_)
+    login_display_delegate_->Login(user_context, SigninSpecifics());
 }
 
 void UserSelectionScreen::Show() {}