arc: Prepare ArcAuthEndpoint flag for finch experiment.

chrome/browser/chromeos/arc/arc_auth_code_fetcher.h

 // Copyright 2016 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.
 
 #ifndef CHROME_BROWSER_CHROMEOS_ARC_ARC_AUTH_CODE_FETCHER_H_
 #define CHROME_BROWSER_CHROMEOS_ARC_ARC_AUTH_CODE_FETCHER_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 10 matching lines @@
 
 namespace arc {
 
 class ArcAuthCodeFetcherDelegate;
 
 class ArcAuthCodeFetcher : public OAuth2TokenService::Consumer,
                            public net::URLFetcherDelegate {
  public:
   ArcAuthCodeFetcher(ArcAuthCodeFetcherDelegate* delegate,
                      net::URLRequestContextGetter* request_context_getter,
-                     Profile* profile,
-                     const std::string& auth_endpoint);
+                     Profile* profile);
   ~ArcAuthCodeFetcher() override;
 
   // OAuth2TokenService::Consumer:
   void OnGetTokenSuccess(const OAuth2TokenService::Request* request,
                          const std::string& access_token,
                          const base::Time& expiration_time) override;
   void OnGetTokenFailure(const OAuth2TokenService::Request* request,
                          const GoogleServiceAuthError& error) override;
 
   // net::URLFetcherDelegate:
   void OnURLFetchComplete(const net::URLFetcher* source) override;
 
  private:
   void ResetFetchers();
 
   // Unowned pointers.
   ArcAuthCodeFetcherDelegate* const delegate_;
   net::URLRequestContextGetter* const request_context_getter_;
   Profile* const profile_;
 
-  // URL to request auth code.
-  const std::string auth_endpoint_;
-
   std::unique_ptr<OAuth2TokenService::Request> login_token_request_;
   std::unique_ptr<net::URLFetcher> auth_code_fetcher_;
 
   DISALLOW_COPY_AND_ASSIGN(ArcAuthCodeFetcher);
 };
 
 }  // namespace arc
 
 #endif  // CHROME_BROWSER_CHROMEOS_ARC_ARC_AUTH_CODE_FETCHER_H_