This CL replaces e-mail with AccountId in wallpaper manager code.

chrome/browser/chromeos/login/ui/webui_login_display.h

Index: chrome/browser/chromeos/login/ui/webui_login_display.h
diff --git a/chrome/browser/chromeos/login/ui/webui_login_display.h b/chrome/browser/chromeos/login/ui/webui_login_display.h
index 3dc8c90deff1e2c4d626085cbac3b24d00b298c4..a06ac1cc0d4f1ecdf60ef38e01b9d8516f3779e2 100644
--- a/chrome/browser/chromeos/login/ui/webui_login_display.h
+++ b/chrome/browser/chromeos/login/ui/webui_login_display.h
@@ -64,7 +64,7 @@ class WebUILoginDisplay : public LoginDisplay,
 
   void OnSigninScreenReady() override;
   void CancelUserAdding() override;
-  void LoadWallpaper(const std::string& username) override;
+  void LoadWallpaper(const AccountId& account_id) override;
   void LoadSigninWallpaper() override;
   void ShowEnterpriseEnrollmentScreen() override;
   void ShowEnableDebuggingScreen() override;