Add a mode to OAuth2MintTokenFlow that fetches the messages to show to the user.

chrome/common/net/gaia/oauth2_api_call_flow.h

 // 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.
 
 #ifndef CHROME_COMMON_NET_GAIA_OAUTH2_API_CALL_FLOW_H_
 #define CHROME_COMMON_NET_GAIA_OAUTH2_API_CALL_FLOW_H_
 
 #include <string>
 
 #include "base/memory/scoped_ptr.h"
@@ skipping 32 matching lines @@
   // the first step (of trying an existing access token).
   OAuth2ApiCallFlow(
       net::URLRequestContextGetter* context,
       const std::string& refresh_token,
       const std::string& access_token,
       const std::vector<std::string>& scopes);
 
   virtual ~OAuth2ApiCallFlow();
 
   // Start the flow.
-  void Start();
+  virtual void Start();
 
   // OAuth2AccessTokenFetcher implementation.
   virtual void OnGetTokenSuccess(const std::string& access_token) OVERRIDE;
   virtual void OnGetTokenFailure(const GoogleServiceAuthError& error) OVERRIDE;
 
   // content::URLFetcherDelegate implementation.
   virtual void OnURLFetchComplete(const content::URLFetcher* source) OVERRIDE;
 
  protected:
   // Template methods for sub-classes.
@@ skipping 53 matching lines @@
   // Whether we have already tried minting an access token once.
   bool tried_mint_access_token_;
 
   scoped_ptr<content::URLFetcher> url_fetcher_;
   scoped_ptr<OAuth2AccessTokenFetcher> oauth2_access_token_fetcher_;
 
   DISALLOW_COPY_AND_ASSIGN(OAuth2ApiCallFlow);
 };
 
 #endif  // CHROME_COMMON_NET_GAIA_OAUTH2_API_CALL_FLOW_H_