[UserClassifier] Inject a clock

components/ntp_snippets/user_classifier.h

 // Copyright 2016 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_NTP_SNIPPETS_USER_CLASSIFIER_H_
 #define COMPONENTS_NTP_SNIPPETS_USER_CLASSIFIER_H_
 
+#include <memory>
 #include <string>
 
 #include "base/macros.h"
-#include "base/time/time.h"
 
 class PrefRegistrySimple;
 class PrefService;
 
+namespace base {
+class Clock;
+}  // namespace base
+
 namespace ntp_snippets {
 
 // Collects data about user usage patterns of content suggestions, computes
 // long-term user metrics locally using pref, and reports the metrics to UMA.
 // Based on these long-term user metrics, it classifies the user in a UserClass.
 class UserClassifier {
  public:
   // Enumeration listing user classes
   enum class UserClass {
     RARE_NTP_USER,
@@ skipping 19 matching lines @@
     // Home, this coincides with NTP_OPENED.
     SUGGESTIONS_SHOWN,  // When the content suggestions are shown to the user -
                         // in the current implementation when the user scrolls
                         // below the fold.
     SUGGESTIONS_USED,   // When the user clicks on some suggestions or on some
                         // "More" button.
     COUNT               // Keep this as the last element.
   };
 
   // The provided |pref_service| may be nullptr in unit-tests.
-  explicit UserClassifier(PrefService* pref_service);
+  UserClassifier(PrefService* pref_service, std::unique_ptr<base::Clock> clock);
   ~UserClassifier();
 
   // Registers profile prefs for all metrics. Called from browser_prefs.cc.
   static void RegisterProfilePrefs(PrefRegistrySimple* registry);
 
   // Informs the UserClassifier about a new event for |metric|. The
   // classification is based on these calls.
   void OnEvent(Metric metric);
 
   // Get the estimate average length of the interval between two successive
@@ skipping 20 matching lines @@
   // return 0.
   double GetHoursSinceLastTime(Metric metric) const;
   bool HasLastTime(Metric metric) const;
   void SetLastTimeToNow(Metric metric);
 
   double GetMetricValue(Metric metric) const;
   void SetMetricValue(Metric metric, double metric_value);
   void ClearMetricValue(Metric metric);
 
   PrefService* pref_service_;
+  std::unique_ptr<base::Clock> clock_;
 
   // Params of the metric.
   const double discount_rate_per_hour_;
   const double min_hours_;
   const double max_hours_;
 
   // Params of the classification.
   const double active_consumer_clicks_at_least_once_per_hours_;
   const double rare_user_opens_ntp_at_most_once_per_hours_;
 
   DISALLOW_COPY_AND_ASSIGN(UserClassifier);
 };
 
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_USER_CLASSIFIER_H_