Implement CryptAuthAccessTokenFetcher.

components/proximity_auth/cryptauth/cryptauth_account_token_fetcher.h

Index: components/proximity_auth/cryptauth/cryptauth_account_token_fetcher.h
diff --git a/components/proximity_auth/cryptauth/cryptauth_account_token_fetcher.h b/components/proximity_auth/cryptauth/cryptauth_account_token_fetcher.h
new file mode 100644
index 0000000000000000000000000000000000000000..717378c2087bdae836c7a82e3019eec5d3b1a100
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+++ b/components/proximity_auth/cryptauth/cryptauth_account_token_fetcher.h
@@ -0,0 +1,56 @@
+// Copyright 2014 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 COMPONENTS_PROXIMITY_AUTH_CRYPT_AUTH_ACCOUNT_TOKEN_FETCHER_IMPL_H
+#define COMPONENTS_PROXIMITY_AUTH_CRYPT_AUTH_ACCOUNT_TOKEN_FETCHER_IMPL_H
+
+#include "base/callback.h"
+#include "components/proximity_auth/cryptauth/cryptauth_access_token_fetcher.h"
+#include "google_apis/gaia/oauth2_token_service.h"
+
+namespace proximity_auth {
+
+// Implementation of CryptAuthAccessTokenFetcher fetching an access token for a
+// given account using the provided OAuth2TokenService.
+class CryptAuthAccountTokenFetcher : public CryptAuthAccessTokenFetcher,
+                                     public OAuth2TokenService::Consumer {
+ public:
+  // |token_service| is not owned, and must outlive this object.
+  CryptAuthAccountTokenFetcher(OAuth2TokenService* token_service,
+                               const std::string& account_id);
+  virtual ~CryptAuthAccountTokenFetcher();
+
+  // CryptAuthAccessTokenFetcher:
+  void FetchAccessToken(const AccessTokenCallback& callback) override;
+
+ private:
+  // 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;
+
+  // System service that caches and fetches tokens for a given account.
+  // Not owned.
+  OAuth2TokenService* token_service_;
+
+  // The account id for whom to mint the token.
+  std::string account_id_;
+
+  // True if FetchAccessToken() has been called.
+  bool fetch_started_;
+
+  // Stores the request from |token_service_| to mint the token.
+  scoped_ptr<OAuth2TokenService::Request> token_request_;
+
+  // Callback to invoke when the token fetch succeeds or fails.
+  AccessTokenCallback callback_;
+
+  DISALLOW_COPY_AND_ASSIGN(CryptAuthAccountTokenFetcher);
+};
+
+}  // namespace proximity_auth
+
+#endif  // COMPONENTS_PROXIMITY_AUTH_CRYPT_AUTH_ACCESS_TOKEN_FETCHER_IMPL_H