Refactor CryptAuth component to be more testable.

components/proximity_auth/cryptauth/cryptauth_account_token_fetcher.cc

-// 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.
-
-#include "components/proximity_auth/cryptauth/cryptauth_account_token_fetcher.h"
-
-namespace proximity_auth {
-
-namespace {
-
-// Returns the set of OAuth2 scopes that CryptAuth uses.
-OAuth2TokenService::ScopeSet GetScopes() {
-  OAuth2TokenService::ScopeSet scopes;
-  scopes.insert("https://www.googleapis.com/auth/cryptauth");
-  return scopes;
-}
-
-}  // namespace
-
-CryptAuthAccountTokenFetcher::CryptAuthAccountTokenFetcher(
-    OAuth2TokenService* token_service,
-    const std::string& account_id)
-    : OAuth2TokenService::Consumer("cryptauth_account_token_fetcher"),
-      token_service_(token_service),
-      account_id_(account_id),
-      fetch_started_(false) {
-}
-
-CryptAuthAccountTokenFetcher::~CryptAuthAccountTokenFetcher() {
-}
-
-void CryptAuthAccountTokenFetcher::FetchAccessToken(
-    const AccessTokenCallback& callback) {
-  if (fetch_started_) {
-    LOG(WARNING) << "Create an instance for each token fetched. Do not reuse.";
-    callback.Run(std::string());
-    return;
-  }
-
-  fetch_started_ = true;
-  callback_ = callback;
-  // This request will return a cached result if it is available, saving a
-  // network round trip every time we fetch the access token.
-  token_request_ = token_service_->StartRequest(account_id_, GetScopes(), this);
-}
-
-void CryptAuthAccountTokenFetcher::OnGetTokenSuccess(
-    const OAuth2TokenService::Request* request,
-    const std::string& access_token,
-    const base::Time& expiration_time) {
-  callback_.Run(access_token);
-}
-
-void CryptAuthAccountTokenFetcher::OnGetTokenFailure(
-    const OAuth2TokenService::Request* request,
-    const GoogleServiceAuthError& error) {
-  callback_.Run(std::string());
-}
-
-}  // namespace proximity_auth