[ContentIndex] Re-enable UKM browsertest.

There are metrics that rely on the background recording service, which in
turn uses the history service that runs on its own thread.

That caused that test to be flaky, so this fix creates a test-only
closure that is run after the metric has been recorded to make it
determenistic.

Bug: 998049
Change-Id: I88ead36796ef07fadf348e1da686b5b200c17509
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1783152Reviewed-by: Richard Knoll <knollr@chromium.org>
Commit-Queue: Rayan Kanso <rayankans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#693143}

chrome/browser/content_index/content_index_browsertest.cc

@@ -270,13 +270,7 @@ IN_PROC_BROWSER_TEST_F(ContentIndexTest, UserDeletedEntryDispatchesEvent) {
   EXPECT_TRUE(GetAllItems().empty());
 }
 
-// Flaky almost universally.  http://crbug.com/998049
-#if defined(OS_WIN) || defined(OS_MACOSX) || defined(OS_LINUX)
-#define MAYBE_MetricsCollected DISABLED_MetricsCollected
-#else
-#define MAYBE_MetricsCollected MetricsCollected
-#endif
-IN_PROC_BROWSER_TEST_F(ContentIndexTest, MAYBE_MetricsCollected) {
+IN_PROC_BROWSER_TEST_F(ContentIndexTest, MetricsCollected) {
   // Inititally there is no content.
   {
     base::HistogramTester histogram_tester;
@@ -290,10 +284,23 @@ IN_PROC_BROWSER_TEST_F(ContentIndexTest, MAYBE_MetricsCollected) {
     base::HistogramTester histogram_tester;
     ukm::TestAutoSetUkmRecorder ukm_recorder;
 
-    RunScript("AddContent('my-id-1')");
-    RunScript("AddContent('my-id-2')");
-    base::RunLoop()
-        .RunUntilIdle();  // Wait for the provider to get the content.
+    {
+      base::RunLoop run_loop;
+      ukm_recorder.SetOnAddEntryCallback(
+          ukm::builders::ContentIndex_Added::kEntryName,
+          run_loop.QuitClosure());
+      RunScript("AddContent('my-id-1')");
+      run_loop.Run();
+    }
+    {
+      base::RunLoop run_loop;
+      ukm_recorder.SetOnAddEntryCallback(
+          ukm::builders::ContentIndex_Added::kEntryName,
+          run_loop.QuitClosure());
+      RunScript("AddContent('my-id-2')");
+      run_loop.Run();
+    }
+
     histogram_tester.ExpectBucketCount(
         "ContentIndex.ContentAdded", blink::mojom::ContentCategory::ARTICLE, 2);
 
@@ -317,9 +324,13 @@ IN_PROC_BROWSER_TEST_F(ContentIndexTest, MAYBE_MetricsCollected) {
     base::HistogramTester histogram_tester;
     ukm::TestAutoSetUkmRecorder ukm_recorder;
 
+    base::RunLoop run_loop;
+    ukm_recorder.SetOnAddEntryCallback(
+        ukm::builders::ContentIndex_DeletedByUser::kEntryName,
+        run_loop.QuitClosure());
     provider()->RemoveItem(offline_items().at("my-id-1").id);
     EXPECT_EQ(RunScript("waitForMessageFromServiceWorker()"), "my-id-1");
-    base::RunLoop().RunUntilIdle();
+    run_loop.Run();
 
     histogram_tester.ExpectBucketCount("ContentIndex.ContentDeleteEvent.Find",
                                        blink::ServiceWorkerStatusCode::kOk, 1);

chrome/browser/content_index/content_index_metrics.h

@@ -34,7 +34,7 @@ class ContentIndexMetrics {
   void RecordContentOpened(content::WebContents* web_contents,
                            blink::mojom::ContentCategory category);
 
-  // Records when a Content UIndex entry is deleted by a user.
+  // Records when a Content Index entry is deleted by a user.
   void RecordContentDeletedByUser(const url::Origin& origin);
 
   // Records the number of Content Index entries available when requested.