[ARC] Add browser test of ArcAuthService

chrome/browser/chromeos/arc/auth/arc_background_auth_code_fetcher.cc

Index: chrome/browser/chromeos/arc/auth/arc_background_auth_code_fetcher.cc
diff --git a/chrome/browser/chromeos/arc/auth/arc_background_auth_code_fetcher.cc b/chrome/browser/chromeos/arc/auth/arc_background_auth_code_fetcher.cc
index ed80b1540eebe03abd14cc93bcb5cff9b1c311fc..84c9bd57689f417788189882ccd3872372b48e4f 100644
--- a/chrome/browser/chromeos/arc/auth/arc_background_auth_code_fetcher.cc
+++ b/chrome/browser/chromeos/arc/auth/arc_background_auth_code_fetcher.cc
@@ -12,12 +12,9 @@
 #include "base/json/json_writer.h"
 #include "base/logging.h"
 #include "base/values.h"
-#include "chrome/browser/signin/profile_oauth2_token_service_factory.h"
-#include "chrome/browser/signin/signin_manager_factory.h"
 #include "chrome/browser/ui/ash/multi_user/multi_user_util.h"
 #include "components/signin/core/account_id/account_id.h"
 #include "components/signin/core/browser/profile_oauth2_token_service.h"
-#include "components/signin/core/browser/signin_manager_base.h"
 #include "components/user_manager/known_user.h"
 #include "content/public/browser/browser_context.h"
 #include "content/public/common/url_constants.h"
@@ -57,6 +54,11 @@ ArcBackgroundAuthCodeFetcher::ArcBackgroundAuthCodeFetcher(
 
 ArcBackgroundAuthCodeFetcher::~ArcBackgroundAuthCodeFetcher() = default;
 
+// static
+std::string ArcBackgroundAuthCodeFetcher::GetTokenExchangeEndpoint() {
+  return kEndPoint;
+}
+
 void ArcBackgroundAuthCodeFetcher::Fetch(const FetchCallback& callback) {
   DCHECK(callback_.is_null());
   callback_ = callback;