arc: Prepare ArcAuthEndpoint flag for finch experiment.

chrome/browser/chromeos/arc/arc_auth_code_fetcher.h

Index: chrome/browser/chromeos/arc/arc_auth_code_fetcher.h
diff --git a/chrome/browser/chromeos/arc/arc_auth_code_fetcher.h b/chrome/browser/chromeos/arc/arc_auth_code_fetcher.h
index 751cb25e9e86c5685a4193e6e1ec1080e1416d69..19a2c18fdb3a9093d2d7e2ed3c121702e7ca3036 100644
--- a/chrome/browser/chromeos/arc/arc_auth_code_fetcher.h
+++ b/chrome/browser/chromeos/arc/arc_auth_code_fetcher.h
@@ -29,9 +29,7 @@ namespace arc {
 class ArcAuthCodeFetcher : public OAuth2TokenService::Consumer,
                            public net::URLFetcherDelegate {
  public:
-  ArcAuthCodeFetcher(Profile* profile,
-                     ArcAuthContext* context,
-                     const std::string& auth_endpoint);
+  ArcAuthCodeFetcher(Profile* profile, ArcAuthContext* context);
   ~ArcAuthCodeFetcher() override;
 
   // Starts to fetch the token. On success fetched |auth_token| is passed.
@@ -58,9 +56,6 @@ class ArcAuthCodeFetcher : public OAuth2TokenService::Consumer,
   ArcAuthContext* const context_;
   net::URLRequestContextGetter* request_context_getter_ = nullptr;
 
-  // URL to request auth code.
-  const std::string auth_endpoint_;
-
   FetchCallback callback_;
 
   std::unique_ptr<OAuth2TokenService::Request> login_token_request_;