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

components/signin/core/browser/about_signin_internals.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/signin/core/browser/about_signin_internals.h"
 
 #include "base/command_line.h"
 #include "base/hash.h"
 #include "base/i18n/time_formatting.h"
 #include "base/logging.h"
@@ skipping 36 matching lines @@
                      const std::string& field_time = "") {
   scoped_ptr<base::DictionaryValue> entry(new base::DictionaryValue());
   entry->SetString("label", field_name);
   entry->SetString("status", field_status);
   entry->SetString("time", field_time);
   section_list->Append(entry.release());
 }
 
 void AddCookieEntry(base::ListValue* accounts_list,
                      const std::string& field_email,
+                     const std::string& field_gaia_id,
                      const std::string& field_valid) {
   scoped_ptr<base::DictionaryValue> entry(new base::DictionaryValue());
   entry->SetString("email", field_email);
+  entry->SetString("gaia_id", field_gaia_id);
   entry->SetString("valid", field_valid);
   accounts_list->Append(entry.release());
 }
 
 std::string SigninStatusFieldToLabel(UntimedSigninStatusField field) {
   switch (field) {
     case ACCOUNT_ID:
       return "Account Id";
     case GAIA_ID:
       return "Gaia Id";
@@ skipping 266 matching lines @@
                                                  const std::string& password) {
   NotifyObservers();
 }
 
 void AboutSigninInternals::GoogleSignedOut(const std::string& account_id,
                                            const std::string& username) {
   NotifyObservers();
 }
 
 void AboutSigninInternals::OnGaiaAccountsInCookieUpdated(
-    const std::vector<std::pair<std::string, bool> >& gaia_accounts,
+    const std::vector<gaia::ListedAccount>& gaia_accounts,
     const GoogleServiceAuthError& error) {
   if (error.state() != GoogleServiceAuthError::NONE)
     return;
 
   base::DictionaryValue cookie_status;
   base::ListValue* cookie_info = new base::ListValue();
   cookie_status.Set("cookie_info", cookie_info);
 
   for (size_t i = 0; i < gaia_accounts.size(); ++i) {
     AddCookieEntry(cookie_info,
-                   gaia_accounts[i].first,
-                   gaia_accounts[i].second ? "Valid" : "Invalid");
+                   gaia_accounts[i].raw_email,
+                   gaia_accounts[i].gaia_id,
+                   gaia_accounts[i].valid ? "Valid" : "Invalid");
   }
 
-  if (gaia_accounts.size() == 0)
-    AddCookieEntry(cookie_info, "No Accounts Present.", "");
+  if (gaia_accounts.size() == 0) {
+    AddCookieEntry(cookie_info,
+                   "No Accounts Present.",
+                   std::string(),
+                   std::string());
+  }
 
   // Update the observers that the cookie's accounts are updated.
   FOR_EACH_OBSERVER(AboutSigninInternals::Observer,
                     signin_observers_,
                     OnCookieAccountsFetched(&cookie_status));
 }
 
 AboutSigninInternals::TokenInfo::TokenInfo(
     const std::string& consumer_id,
     const OAuth2TokenService::ScopeSet& scopes)
@@ skipping 219 matching lines @@
   }
 
   for(const std::string& account_id : accounts_in_token_service) {
     base::DictionaryValue* entry = new base::DictionaryValue();
     entry->SetString("accountId", account_id);
     account_info->Append(entry);
   }
 
   return signin_status.Pass();
 }