Create a synthetic field trial for precache.

components/precache/content/precache_manager.h

 // Copyright 2013 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_PRECACHE_CONTENT_PRECACHE_MANAGER_H_
 #define COMPONENTS_PRECACHE_CONTENT_PRECACHE_MANAGER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 39 matching lines @@
 
 namespace syncer {
 class SyncService;
 }
 
 namespace precache {
 
 class PrecacheDatabase;
 class PrecacheUnfinishedWork;
 
+extern const char kPrecacheFieldTrialName[];
+
 // Visible for test.
-extern const char kPrecacheFieldTrialName[];
 extern const char kMinCacheSizeParam[];
 size_t NumTopHosts();
 
 // Class that manages all precaching-related activities. Owned by the
 // BrowserContext that it is constructed for. Use
 // PrecacheManagerFactory::GetForBrowserContext to get an instance of this
 // class. All methods must be called on the UI thread unless indicated
 // otherwise.
 // TODO(sclittle): Delete precache history when browsing history is deleted.
 // http://crbug.com/326549
@@ skipping 40 matching lines @@
   // Returns true if precaching is currently in progress, or false otherwise.
   bool IsPrecaching() const;
 
   // Posts a task to the DB thread to delete all history entries from the
   // database. Does not wait for completion of this task.
   void ClearHistory();
 
   // Update precache about an URL being fetched. Metrics related to precache are
   // updated and any ongoing precache will be cancelled if this is an user
   // initiated request. Should be called on UI thread.
-  void UpdatePrecacheMetricsAndState(const GURL& url,
-                                     const GURL& referrer,
-                                     const base::TimeDelta& latency,
-                                     const base::Time& fetch_time,
-                                     const net::HttpResponseInfo& info,
-                                     int64_t size,
-                                     bool is_user_traffic);
+  void UpdatePrecacheMetricsAndState(
+      const GURL& url,
+      const GURL& referrer,
+      const base::TimeDelta& latency,
+      const base::Time& fetch_time,
+      const net::HttpResponseInfo& info,
+      int64_t size,
+      bool is_user_traffic,
+      const base::Callback<void(base::Time)>& register_synthetic_trial);
 
  private:
   friend class PrecacheManagerTest;
   FRIEND_TEST_ALL_PREFIXES(PrecacheManagerTest, DeleteExpiredPrecacheHistory);
   FRIEND_TEST_ALL_PREFIXES(PrecacheManagerTest,
                            RecordStatsForFetchDuringPrecaching);
   FRIEND_TEST_ALL_PREFIXES(PrecacheManagerTest, RecordStatsForFetchHTTP);
   FRIEND_TEST_ALL_PREFIXES(PrecacheManagerTest, RecordStatsForFetchHTTPS);
   FRIEND_TEST_ALL_PREFIXES(PrecacheManagerTest, RecordStatsForFetchInTopHosts);
   FRIEND_TEST_ALL_PREFIXES(PrecacheManagerTest,
                            RecordStatsForFetchWithEmptyURL);
   FRIEND_TEST_ALL_PREFIXES(PrecacheManagerTest, RecordStatsForFetchWithNonHTTP);
   FRIEND_TEST_ALL_PREFIXES(PrecacheManagerTest,
                            RecordStatsForFetchWithSizeZero);
 
   enum class AllowedType {
     ALLOWED,
     DISALLOWED,
     PENDING
   };
 
   // From KeyedService.
   void Shutdown() override;
 
   // From PrecacheFetcher::PrecacheDelegate.
   void OnDone() override;
 
+  // Registers the precache synthetic field trial for users whom the precache
+  // task was run recently. |last_precache_time| is the last time precache task
+  // was run.
+  void RegisterSyntheticFieldTrial(const base::Time last_precache_time);
+
   // Callback when fetching unfinished work from storage is done.
   void OnGetUnfinishedWorkDone(
       std::unique_ptr<PrecacheUnfinishedWork> unfinished_work);
 
   // From history::HistoryService::TopHosts.
   void OnHostsReceived(const history::TopHostsList& host_counts);
 
   // Initializes and Starts a PrecacheFetcher with unfinished work.
   void InitializeAndStartFetcher();
 
   // From history::HistoryService::TopHosts. Used for the control group, which
   // gets the list of TopHosts for metrics purposes, but otherwise does nothing.
   void OnHostsReceivedThenDone(const history::TopHostsList& host_counts);
 
   // Chain of callbacks for StartPrecaching that make sure that we only precache
   // if there is a cache big enough.
   void PrecacheIfCacheIsBigEnough(
       scoped_refptr<net::URLRequestContextGetter> url_request_context_getter);
   void OnCacheBackendReceived(int net_error_code);
   void OnCacheSizeReceived(int cache_size_bytes);
   void OnCacheSizeReceivedInUIThread(int cache_size_bytes);
 
   // Returns true if precaching is allowed for the browser context.
   AllowedType PrecachingAllowed() const;
 
   // Update precache-related metrics in response to a URL being fetched.
-  void RecordStatsForFetch(const GURL& url,
-                           const GURL& referrer,
-                           const base::TimeDelta& latency,
-                           const base::Time& fetch_time,
-                           const net::HttpResponseInfo& info,
-                           int64_t size);
+  void RecordStatsForFetch(
+      const GURL& url,
+      const GURL& referrer,
+      const base::TimeDelta& latency,
+      const base::Time& fetch_time,
+      const net::HttpResponseInfo& info,
+      int64_t size,
+      const base::Callback<void(base::Time)>& register_synthetic_trial,
+      base::Time last_precache_time);
 
   // Update precache-related metrics in response to a URL being fetched. Called
   // by RecordStatsForFetch() by way of an asynchronous HistoryService callback.
   void RecordStatsForFetchInternal(const GURL& url,
                                    const std::string& referrer_host,
                                    const base::TimeDelta& latency,
                                    const base::Time& fetch_time,
                                    const net::HttpResponseInfo& info,
                                    int64_t size,
                                    int host_rank);
@@ skipping 40 matching lines @@
 
   // Work that hasn't yet finished.
   std::unique_ptr<PrecacheUnfinishedWork> unfinished_work_;
 
   DISALLOW_COPY_AND_ASSIGN(PrecacheManager);
 };
 
 }  // namespace precache
 
 #endif  // COMPONENTS_PRECACHE_CONTENT_PRECACHE_MANAGER_H_