Add prefetch support to AffiliationBackend.

components/password_manager/core/browser/affiliation_service.h

 // Copyright 2015 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_PASSWORD_MANAGER_CORE_BROWSER_AFFILIATION_SERVICE_H_
 #define COMPONENTS_PASSWORD_MANAGER_CORE_BROWSER_AFFILIATION_SERVICE_H_
 
 #include <string>
 
 #include "base/callback.h"
@@ skipping 74 matching lines @@
 //        private:
 //         AffiliationService* service_;
 //         const FacetURI& y_;
 //         CancelPrefetchingHandle cancel_handle_;
 //       };
 class AffiliationService : public KeyedService {
  public:
   typedef base::Callback<void(const AffiliatedFacets& /* results */,
                               bool /* success */)> ResultCallback;
 
-  typedef base::Closure CancelPrefetchingHandle;
-
   // The |backend_task_runner| should be a task runner corresponding to a thread
   // that can take blocking I/O, and is normally Chrome's DB thread.
   AffiliationService(
       scoped_refptr<base::SingleThreadTaskRunner> backend_task_runner);
   ~AffiliationService() override;
 
   // Initializes the service by creating its backend and transferring it to the
   // thread corresponding to |backend_task_runner_|.
   void Initialize(net::URLRequestContextGetter* request_context_getter,
                   const base::FilePath& db_path);
 
   // Looks up facets affiliated with the facet identified by |facet_uri|. If
   // |cached_only| is true, the results will be based solely on prefetched
   // information already stored in the cache. Otherwise, on-demand network
   // requests will be issued if there is no up-to-date data in the cache.
   void GetAffiliations(const FacetURI& facet_uri,
                        bool cached_only,
                        const ResultCallback& result_callback);
 
   // Prefetches affiliation information for the facet identified by |facet_uri|,
-  // and keeps the information fresh by periodic re-fetches (as needed) until at
-  // least |keep_fresh_until|, the returned cancel handle is called, or until
-  // Chrome is shut down, whichever is sooner. It is a supported use-case to
-  // pass base::Time::Max() as |keep_fresh_until|.
+  // and keeps the information fresh by periodic re-fetches (as needed) until
+  // the clock strikes |keep_fresh_until| (exclusive), until a matching call to
+  // CancelPrefetch(), or until Chrome is shut down, whichever is sooner. It is
+  // a supported use-case to pass base::Time::Max() as |keep_fresh_until|.
   //
   // Canceling can be useful when a password is deleted, so that resources are
   // no longer wasted on repeatedly refreshing affiliation information. Note
   // that canceling will not blow away data already stored in the cache unless
   // it becomes stale.
-  CancelPrefetchingHandle Prefetch(const FacetURI& facet_uri,
-                                   const base::Time& keep_fresh_until);
+  void Prefetch(const FacetURI& facet_uri, const base::Time& keep_fresh_until);
+
+  // Cancels the corresponding prefetch command, i.e., the one issued for the
+  // same |facet_uri| and with the same |keep_fresh_until|.
+  void CancelPrefetch(const FacetURI& facet_uri,
+                      const base::Time& keep_fresh_until);
 
   // Wipes results of on-demand fetches and expired prefetches from the cache,
   // but retains information corresponding to facets that are being kept fresh.
   // As no required data is deleted, there will be no network requests directly
   // triggered by this call.
   void TrimCache();
 
  private:
-  // Cancels the corresponding prefetch command, i.e., the one issued for the
-  // same |facet_uri| and with the same |keep_fresh_until|.
-  void CancelPrefetch(const FacetURI& facet_uri, const base::Time&);
-
   // The backend, owned by this AffiliationService instance, but living on the
   // DB thread. It will be deleted asynchronously during shutdown on the DB
   // thread, so it will outlive |this| along with all its in-flight tasks.
   AffiliationBackend* backend_;
 
   // TaskRunner to be used to run the |backend_| (usually the DB thread).
   scoped_refptr<base::SingleThreadTaskRunner> backend_task_runner_;
 
   base::ThreadChecker thread_checker_;
   base::WeakPtrFactory<AffiliationService> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(AffiliationService);
 };
 
 }  // namespace password_manager
 
 #endif  // COMPONENTS_PASSWORD_MANAGER_CORE_BROWSER_AFFILIATION_SERVICE_H_