Implement an observer interface for the site engagement service.

chrome/browser/engagement/site_engagement_service.cc

Index: chrome/browser/engagement/site_engagement_service.cc
diff --git a/chrome/browser/engagement/site_engagement_service.cc b/chrome/browser/engagement/site_engagement_service.cc
index fa8f699fa73d44699dceb25ff8fd40be2f399503..4e8b233bb3d9c0588080555460797d3478ed7105 100644
--- a/chrome/browser/engagement/site_engagement_service.cc
+++ b/chrome/browser/engagement/site_engagement_service.cc
@@ -209,6 +209,14 @@ bool SiteEngagementService::IsEngagementAtLeast(
   return false;
 }
 
+void SiteEngagementService::AddObserver(SiteEngagementObserver* observer) {
+  observer_list_.AddObserver(observer);
+}
+
+void SiteEngagementService::RemoveObserver(SiteEngagementObserver* observer) {
+  observer_list_.RemoveObserver(observer);
+}
+
 void SiteEngagementService::ResetScoreForURL(const GURL& url, double score) {
   ResetScoreAndAccessTimesForURL(url, score, nullptr);
 }
@@ -282,6 +290,8 @@ void SiteEngagementService::AddPoints(const GURL& url, double points) {
         url, GURL(), CONTENT_SETTINGS_TYPE_SITE_ENGAGEMENT, std::string(),
         score_dict.release());
   }
+  FOR_EACH_OBSERVER(SiteEngagementObserver, observer_list_,
+                    OnEngagementIncreased(this, url, score.GetScore()));
 }
 
 void SiteEngagementService::AfterStartupTask() {
@@ -365,6 +375,25 @@ double SiteEngagementService::GetMedianEngagement(
     return (scores[mid - 1] + scores[mid]) / 2;
 }
 
+double SiteEngagementService::GetScoreForEngagementLevel(
+    EngagementLevel level) const {
+  switch (level) {
+    case ENGAGEMENT_LEVEL_NONE:
+      return 0;
+    case ENGAGEMENT_LEVEL_LOW:
+      return SiteEngagementScore::GetMinimumEngagementIncrement();
+    case ENGAGEMENT_LEVEL_MEDIUM:
+      return SiteEngagementScore::GetMediumEngagementBoundary();
+    case ENGAGEMENT_LEVEL_HIGH:
+      return SiteEngagementScore::GetHighEngagementBoundary();
+    case ENGAGEMENT_LEVEL_MAX:
+      return SiteEngagementScore::kMaxPoints;
+    default:
+      NOTREACHED();
+      return 0;
+  }
+}
+
 void SiteEngagementService::HandleMediaPlaying(const GURL& url,
                                                bool is_hidden) {
   SiteEngagementMetrics::RecordEngagement(