Add a SiteEngagementEvictionPolicy.

chrome/browser/engagement/site_engagement_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 CHROME_BROWSER_ENGAGEMENT_SITE_ENGAGEMENT_SERVICE_H_
 #define CHROME_BROWSER_ENGAGEMENT_SITE_ENGAGEMENT_SERVICE_H_
 
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
-#include "base/memory/scoped_ptr.h"
 #include "base/time/default_clock.h"
 #include "base/time/time.h"
 #include "components/keyed_service/core/keyed_service.h"
 
 namespace base {
 class DictionaryValue;
 }
 
 class GURL;
 class Profile;
@@ skipping 56 matching lines @@
   double points_added_today_;
 
   // The last time the score was updated for engagement. Used in conjunction
   // with |points_added_today_| to avoid adding more than kMaxPointsPerDay on
   // any one day.
   base::Time last_engagement_time_;
 
   DISALLOW_COPY_AND_ASSIGN(SiteEngagementScore);
 };
 
+class SiteEngagementScoreProvider {
+ public:
+  // Returns a non-negative integer representing the engagement score of the
+  // origin for this URL.
+  virtual int GetScore(const GURL& url) = 0;
+
+  // Returns the sum of engagement points awarded to all sites.
+  virtual int GetTotalEngagementPoints() = 0;
+};
+
 // Stores and retrieves the engagement score of an origin.
 //
 // An engagement score is a positive integer that represents how much a user has
 // engaged with an origin - the higher it is, the more engagement the user has
 // had with this site recently.
 //
 // Positive user activity, such as visiting the origin often and adding it to
 // the homescreen, will increase the site engagement score. Negative activity,
 // such as rejecting permission prompts or not responding to notifications, will
 // decrease the site engagement score.
-class SiteEngagementService : public KeyedService {
+class SiteEngagementService : public KeyedService,
+                              public SiteEngagementScoreProvider {
  public:
   static SiteEngagementService* Get(Profile* profile);
 
   // Returns whether or not the SiteEngagementService is enabled.
   static bool IsEnabled();
 
   explicit SiteEngagementService(Profile* profile);
   ~SiteEngagementService() override;
 
   // Update the karma score of the origin matching |url| for user navigation.
   void HandleNavigation(const GURL& url);
 
-  // Returns a non-negative integer representing the engagement score of the
-  // origin for this URL.
-  int GetScore(const GURL& url);
-
-  // Returns the sum of engagement points awarded to all sites.
-  int GetTotalEngagementPoints();
+  // Overridden from SiteEngagementScoreProvider:
+  int GetScore(const GURL& url) override;
+  int GetTotalEngagementPoints() override;
 
  private:
   Profile* profile_;
 
   // The clock used to vend times.
   base::DefaultClock clock_;
 
   DISALLOW_COPY_AND_ASSIGN(SiteEngagementService);
 };
 
 #endif  // CHROME_BROWSER_ENGAGEMENT_SITE_ENGAGEMENT_SERVICE_H_