Make Site Engagement behave for adding 0 points.

chrome/browser/engagement/site_engagement_service_unittest.cc

Index: chrome/browser/engagement/site_engagement_service_unittest.cc
diff --git a/chrome/browser/engagement/site_engagement_service_unittest.cc b/chrome/browser/engagement/site_engagement_service_unittest.cc
index 0a594dbf52c9db07675f18e11ae051e3ca2bdb3c..a7d2db4645e4fb92a9576f90e0e7192c0735c047 100644
--- a/chrome/browser/engagement/site_engagement_service_unittest.cc
+++ b/chrome/browser/engagement/site_engagement_service_unittest.cc
@@ -1459,9 +1459,17 @@ TEST_F(SiteEngagementServiceTest, LastEngagementTime) {
   EXPECT_EQ(rebased_time, last_engagement_time);
   EXPECT_EQ(rebased_time, service->GetLastEngagementTime());
 
-  // Add some more points and ensure the value is persisted.
+  // Adding 0 points shouldn't update the last engagement time.
   base::Time later_in_day = current_day + base::TimeDelta::FromSeconds(30);
   clock->SetNow(later_in_day);
+  service->AddPoints(origin, 0);
+
+  last_engagement_time = base::Time::FromInternalValue(
+      profile()->GetPrefs()->GetInt64(prefs::kSiteEngagementLastUpdateTime));
+  EXPECT_EQ(rebased_time, last_engagement_time);
+  EXPECT_EQ(rebased_time, service->GetLastEngagementTime());
+
+  // Add some more points and ensure the value is persisted.
   service->AddPoints(origin, 3);
 
   last_engagement_time = base::Time::FromInternalValue(