Implement an observer interface for the site engagement service.

chrome/browser/engagement/site_engagement_score.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 CHROME_BROWSER_ENGAGEMENT_SITE_ENGAGEMENT_SCORE_H_
 #define CHROME_BROWSER_ENGAGEMENT_SITE_ENGAGEMENT_SCORE_H_
 
 #include <memory>
 
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/time/time.h"
 #include "base/values.h"
 #include "url/gurl.h"
 
 namespace base {
 class Clock;
 }
 
 class HostContentSettingsMap;
 
 class SiteEngagementScore {
  public:
-  // The parameters which can be varied via field trial. All "points" values
-  // should be appended to the end of the enum prior to MAX_VARIATION.
+  // The parameters which can be varied via field trial.
   enum Variation {
     // The maximum number of points that can be accrued in one day.
     MAX_POINTS_PER_DAY = 0,
 
     // The period over which site engagement decays.
     DECAY_PERIOD_IN_DAYS,
 
     // The number of points to decay per period.
     DECAY_POINTS,
 
@@ skipping 150 matching lines @@
   // The origin this score represents.
   GURL origin_;
 
   // The settings map to write this score to when Commit() is called.
   HostContentSettingsMap* settings_map_;
 
   DISALLOW_COPY_AND_ASSIGN(SiteEngagementScore);
 };
 
 #endif  // CHROME_BROWSER_ENGAGEMENT_SITE_ENGAGEMENT_SCORE_H_