Implement an observer interface for the site engagement service.

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 e43d6d63f38d409f1452d918097426f4ac572b93..f920e45a8456faaa32a07500fe35412428dd75f9 100644
--- a/chrome/browser/engagement/site_engagement_service_unittest.cc
+++ b/chrome/browser/engagement/site_engagement_service_unittest.cc
@@ -97,6 +97,40 @@ std::unique_ptr<KeyedService> BuildTestHistoryService(
 
 }  // namespace
 
+class ObserverTester : public SiteEngagementObserver {
+ public:
+  ObserverTester(SiteEngagementService* service, const GURL& url, double score)
+      : SiteEngagementObserver(service),
+        url_(url),
+        score_(score),
+        callback_called_(false),
+        run_loop_() {}
+
+  void OnEngagementIncreased(const SiteEngagementService* service,
+                             const GURL& url,
+                             double score) override {
+    EXPECT_EQ(url_, url);
+    EXPECT_EQ(score_, score);
+    set_callback_called(true);
+    run_loop_.Quit();
+  }
+
+  void Wait() { run_loop_.Run(); }
+
+  bool callback_called() { return callback_called_; }
+  void set_callback_called(bool callback_called) {
+    callback_called_ = callback_called;
+  }
+
+ private:
+  GURL url_;
+  double score_;
+  bool callback_called_;
+  base::RunLoop run_loop_;
+
+  DISALLOW_COPY_AND_ASSIGN(ObserverTester);
+};
+
 class SiteEngagementServiceTest : public ChromeRenderViewHostTestHarness {
  public:
   void SetUp() override {
@@ -983,6 +1017,54 @@ TEST_F(SiteEngagementServiceTest, EngagementLevel) {
       url2, SiteEngagementService::ENGAGEMENT_LEVEL_MAX));
 }
 
+TEST_F(SiteEngagementServiceTest, Observers) {
+  SiteEngagementService* service = SiteEngagementService::Get(profile());
+
+  GURL url_score_1("http://www.google.com/maps");
+  GURL url_score_2("http://www.google.com/drive");
+  GURL url_score_3("http://www.google.com/");
+  GURL url_not_called("https://www.google.com/");
+
+  // Create an observer and Observe(nullptr).
+  ObserverTester tester_not_called(service, url_not_called, 1);
+  tester_not_called.Observe(nullptr);
+
+  {
+    // Create an observer for score 1.
+    ObserverTester tester(service, url_score_1, 1);
+    service->AddPoints(url_score_1, 1);
+    tester.Wait();
+    EXPECT_TRUE(tester.callback_called());
+    EXPECT_FALSE(tester_not_called.callback_called());
+    tester.Observe(nullptr);
+  }
+
+  {
+    // Update observer for score 1.05
+    ObserverTester tester(service, url_score_2, 1.05);
+    service->AddPoints(url_score_2, 0.05);
+    tester.Wait();
+    EXPECT_TRUE(tester.callback_called());
+    EXPECT_FALSE(tester_not_called.callback_called());
+    tester.Observe(nullptr);
+  }
+
+  // Add two observers for score 1.55.
+  {
+    ObserverTester tester_1(service, url_score_3, 1.55);
+    ObserverTester tester_2(service, url_score_3, 1.55);
+    service->AddPoints(url_score_3, 0.5);
+    tester_1.Wait();
+    tester_2.Wait();
+
+    EXPECT_TRUE(tester_1.callback_called());
+    EXPECT_TRUE(tester_2.callback_called());
+    EXPECT_FALSE(tester_not_called.callback_called());
+    tester_1.Observe(nullptr);
+    tester_2.Observe(nullptr);
+  }
+}
+
 TEST_F(SiteEngagementServiceTest, ScoreDecayHistograms) {
   base::SimpleTestClock* clock = new base::SimpleTestClock();
   std::unique_ptr<SiteEngagementService> service(