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 81 matching lines @@
   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);
+  virtual int GetScore(const GURL& url);
 
   // Returns the sum of engagement points awarded to all sites.
-  int GetTotalEngagementPoints();
+  virtual int GetTotalEngagementPoints();
 
  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_