ListAccounts will return the Gaia ID as well as the email of the account.

chrome/browser/ui/webui/signin_internals_ui.cc

Index: chrome/browser/ui/webui/signin_internals_ui.cc
diff --git a/chrome/browser/ui/webui/signin_internals_ui.cc b/chrome/browser/ui/webui/signin_internals_ui.cc
index a709e4065c8858041c87abe183540d74ad4540d5..a14e6c610e72a2abe6f90a05d591a936dc7cb4ce 100644
--- a/chrome/browser/ui/webui/signin_internals_ui.cc
+++ b/chrome/browser/ui/webui/signin_internals_ui.cc
@@ -73,7 +73,7 @@ bool SignInInternalsUI::OverrideHandleWebUIMessage(
           "chrome.signin.getSigninInfo.handleReply",
           *about_signin_internals->GetSigninStatus());
 
-      std::vector<std::pair<std::string, bool>> cookie_accounts;
+      std::vector<gaia::ListedAccount> cookie_accounts;
       GaiaCookieManagerService* cookie_manager_service =
           GaiaCookieManagerServiceFactory::GetForProfile(profile);
       if (cookie_manager_service->ListAccounts(&cookie_accounts)) {