Remove origins with zero engagement

When urls are removed from chrome://history, the site-engagement score
is not removed if it reaches zero. This CL fixes the issue as it is not
neccessary to keep a score of zero around.

Bug: 838875
Change-Id: Ia580ee49f2c4df8cda46f33c36b6551580dafef7
Reviewed-on: https://chromium-review.googlesource.com/1046765Reviewed-by: calamity <calamity@chromium.org>
Commit-Queue: Christian Dullweber <dullweber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#556740}

chrome/browser/engagement/site_engagement_service.cc

@@ -641,6 +641,9 @@ void SiteEngagementService::GetCountsAndLastVisitForOriginsComplete(
   base::Time four_weeks_ago =
       now - base::TimeDelta::FromDays(FOUR_WEEKS_IN_DAYS);
 
+  HostContentSettingsMap* settings_map =
+      HostContentSettingsMapFactory::GetForProfile(profile_);
+
   for (const auto& origin_to_count : remaining_origins) {
     GURL origin = origin_to_count.first;
     // It appears that the history service occasionally sends bad URLs to us.
@@ -657,6 +660,14 @@ void SiteEngagementService::GetCountsAndLastVisitForOriginsComplete(
     if ((expired && remaining != 0) || deleted == 0)
       continue;
 
+    // Remove origins that have no urls left.
+    if (remaining == 0) {
+      settings_map->SetWebsiteSettingDefaultScope(
+          origin, GURL(), CONTENT_SETTINGS_TYPE_SITE_ENGAGEMENT,
+          content_settings::ResourceIdentifier(), nullptr);
+      continue;
+    }
+
     // Remove engagement proportional to the urls expired from the origin's
     // entire history.
     double proportion_remaining =

chrome/browser/engagement/site_engagement_service_unittest.cc

@@ -1134,6 +1134,7 @@ TEST_F(SiteEngagementServiceTest, CleanupOriginsOnHistoryDeletion) {
   AssertInRange(5.0, service_->GetScore(origin2));
   AssertInRange(5.0, service_->GetScore(origin3));
   AssertInRange(5.0, service_->GetScore(origin4));
+  EXPECT_EQ(4U, service_->GetAllDetails().size());
 
   {
     SiteEngagementChangeWaiter waiter(profile());
@@ -1154,6 +1155,7 @@ TEST_F(SiteEngagementServiceTest, CleanupOriginsOnHistoryDeletion) {
     AssertInRange(5.0, service_->GetScore(origin3));
     AssertInRange(2.5, service_->GetScore(origin4));
     AssertInRange(9.5, service_->GetTotalEngagementPoints());
+    EXPECT_EQ(3U, service_->GetAllDetails().size());
   }
 
   {
@@ -1177,6 +1179,7 @@ TEST_F(SiteEngagementServiceTest, CleanupOriginsOnHistoryDeletion) {
     AssertInRange(5.0, service_->GetScore(origin3));
     AssertInRange(2.5, service_->GetScore(origin4));
     AssertInRange(8.5, service_->GetTotalEngagementPoints());
+    EXPECT_EQ(3U, service_->GetAllDetails().size());
   }
 
   {
@@ -1199,6 +1202,7 @@ TEST_F(SiteEngagementServiceTest, CleanupOriginsOnHistoryDeletion) {
     AssertInRange(5.0, service_->GetScore(origin3));
     AssertInRange(2.5, service_->GetScore(origin4));
     AssertInRange(7.5, service_->GetTotalEngagementPoints());
+    EXPECT_EQ(2U, service_->GetAllDetails().size());
   }
 }