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

chrome/browser/signin/fake_gaia_cookie_manager_service.cc

 // Copyright 2015 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 "chrome/browser/signin/fake_gaia_cookie_manager_service.h"
 
 #include "base/strings/stringprintf.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/signin/chrome_signin_client_factory.h"
 #include "chrome/browser/signin/profile_oauth2_token_service_factory.h"
@@ skipping 43 matching lines @@
       net::URLRequestStatus::SUCCESS);
 }
 
 void FakeGaiaCookieManagerService::SetListAccountsResponseOneAccount(
     const char* account) {
   DCHECK(url_fetcher_factory_);
   url_fetcher_factory_->SetFakeResponse(
       GaiaUrls::GetInstance()->ListAccountsURLWithSource(
           GaiaConstants::kChromeSource),
       base::StringPrintf(
-          "[\"f\", [[\"b\", 0, \"n\", \"%s\", \"p\", 0, 0, 0, 0, 1]]]",
+          "[\"f\", [[\"b\", 0, \"n\", \"%s\", \"p\", 0, 0, 0, 0, 1, \"22\"]]]",
           account),
       net::HTTP_OK,
       net::URLRequestStatus::SUCCESS);
 }
 
 void FakeGaiaCookieManagerService::SetListAccountsResponseOneAccountWithExpiry(
     const char* account, bool expired) {
   DCHECK(url_fetcher_factory_);
   url_fetcher_factory_->SetFakeResponse(
       GaiaUrls::GetInstance()->ListAccountsURLWithSource(
           GaiaConstants::kChromeSource),
       base::StringPrintf(
-          "[\"f\", [[\"b\", 0, \"n\", \"%s\", \"p\", 0, 0, 0, 0, %d]]]",
+          "[\"f\", [[\"b\", 0, \"n\", \"%s\", \"p\", 0, 0, 0, 0, %d, \"22\"]]]",
           account, expired ? 0 : 1),
       net::HTTP_OK,
       net::URLRequestStatus::SUCCESS);
 }
 
 void FakeGaiaCookieManagerService::SetListAccountsResponseTwoAccounts(
     const char* account1, const char* account2) {
   DCHECK(url_fetcher_factory_);
   url_fetcher_factory_->SetFakeResponse(
       GaiaUrls::GetInstance()->ListAccountsURLWithSource(
           GaiaConstants::kChromeSource),
       base::StringPrintf(
-          "[\"f\", [[\"b\", 0, \"n\", \"%s\", \"p\", 0, 0, 0, 0, 1], "
-          "[\"b\", 0, \"n\", \"%s\", \"p\", 0, 0, 0, 0, 1]]]",
+          "[\"f\", [[\"b\", 0, \"n\", \"%s\", \"p\", 0, 0, 0, 0, 1, \"22\"], "
+          "[\"b\", 0, \"n\", \"%s\", \"p\", 0, 0, 0, 0, 1, \"24\"]]]",
           account1, account2),
       net::HTTP_OK,
       net::URLRequestStatus::SUCCESS);
 }
 
 void FakeGaiaCookieManagerService::SetListAccountsResponseTwoAccountsWithExpiry(
     const char* account1, bool account1_expired,
     const char* account2, bool account2_expired) {
   DCHECK(url_fetcher_factory_);
   url_fetcher_factory_->SetFakeResponse(
       GaiaUrls::GetInstance()->ListAccountsURLWithSource(
           GaiaConstants::kChromeSource),
       base::StringPrintf(
-          "[\"f\", [[\"b\", 0, \"n\", \"%s\", \"p\", 0, 0, 0, 0, %d], "
-          "[\"b\", 0, \"n\", \"%s\", \"p\", 0, 0, 0, 0, %d]]]",
+          "[\"f\", [[\"b\", 0, \"n\", \"%s\", \"p\", 0, 0, 0, 0, %d, \"28\"], "
+          "[\"b\", 0, \"n\", \"%s\", \"p\", 0, 0, 0, 0, %d, \"29\"]]]",
           account1, account1_expired ? 0 : 1,
           account2, account2_expired ? 0 : 1),
       net::HTTP_OK,
       net::URLRequestStatus::SUCCESS);
 }
 
 // static
 KeyedService* FakeGaiaCookieManagerService::Build(
     content::BrowserContext* context) {
   Profile* profile = Profile::FromBrowserContext(context);
   FakeGaiaCookieManagerService* service = new FakeGaiaCookieManagerService(
       ProfileOAuth2TokenServiceFactory::GetForProfile(profile),
       GaiaConstants::kChromeSource,
       ChromeSigninClientFactory::GetForProfile(profile));
   return service;
 }