Add a flow class to abstract all the details of minting a token for an app.

chrome/common/net/gaia/oauth2_access_token_fetcher.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_ACCESS_TOKEN_FETCHER_H_
 #define CHROME_COMMON_NET_GAIA_OAUTH2_ACCESS_TOKEN_FETCHER_H_
 #pragma once
 
 #include <string>
 
@@ skipping 34 matching lines @@
   OAuth2AccessTokenFetcher(OAuth2AccessTokenConsumer* consumer,
                            net::URLRequestContextGetter* getter);
   virtual ~OAuth2AccessTokenFetcher();
 
   // Starts the flow with the given parameters.
   // |scopes| can be empty. If it is empty then the access token will have the
   // same scope as the refresh token. If not empty, then access token will have
   // the scopes specified. In this case, the access token will successfully be
   // generated only if refresh token has login scope of a list of scopes that is
   // a super-set of the specified scopes.
-  void Start(const std::string& client_id,
-             const std::string& client_secret,
-             const std::string& refresh_token,
-             const std::vector<std::string>& scopes);
+  virtual void Start(const std::string& client_id,
+                     const std::string& client_secret,
+                     const std::string& refresh_token,
+                     const std::vector<std::string>& scopes);
 
   void CancelRequest();
 
   // Implementation of content::URLFetcherDelegate
   virtual void OnURLFetchComplete(const content::URLFetcher* source) OVERRIDE;
 
  private:
   enum State {
     INITIAL,
     GET_ACCESS_TOKEN_STARTED,
@@ skipping 34 matching lines @@
   friend class OAuth2AccessTokenFetcherTest;
   FRIEND_TEST_ALL_PREFIXES(OAuth2AccessTokenFetcherTest,
                            ParseGetAccessTokenResponse);
   FRIEND_TEST_ALL_PREFIXES(OAuth2AccessTokenFetcherTest,
                            MakeGetAccessTokenBody);
 
   DISALLOW_COPY_AND_ASSIGN(OAuth2AccessTokenFetcher);
 };
 
 #endif  // CHROME_COMMON_NET_GAIA_OAUTH2_ACCESS_TOKEN_FETCHER_H_