[Merge to M110] Prerender: Record events on PrerenderPageLoadMetricsO…

…bserver in UMA

This UMA is used for debugging the issue. From this UMA, it's expected
that we understand...

- whether prerender page load events are notified to the observer, and
- whether the events are ignored as the prerendered page gets
  backgrounded.

Intentionally this UMA doesn't record observer events per trigger type
(e.g., SpeculationRules) because some functions can be called before
PrerenderPageLoadMetricsObserver::trigger_type_ is set (e.g., when
OnComplete() called from the destructor of PageLoadTracker before
prerender activation).

(cherry picked from commit 1ea2057)

Bug: 1379491
Change-Id: Ibecacc386142397a8dd9ddc298b9adccaa80cc63
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4194898
Reviewed-by: Takashi Toyoshima <toyoshim@chromium.org>
Reviewed-by: Asami Doi <asamidoi@chromium.org>
Commit-Queue: Hiroki Nakagawa <nhiroki@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#1097400}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4206627
Commit-Queue: Takashi Toyoshima <toyoshim@chromium.org>
Auto-Submit: Hiroki Nakagawa <nhiroki@chromium.org>
Cr-Commit-Position: refs/branch-heads/5481@{#811}
Cr-Branched-From: 130f3e4-refs/heads/main@{#1084008}

chrome/browser/page_load_metrics/observers/prerender_page_load_metrics_observer_browsertest.cc

@@ -66,6 +66,12 @@ class PrerenderPageLoadMetricsObserverBrowserTest
 
  protected:
   void CheckResponsivenessMetrics(const GURL& url) {
+    histogram_tester().ExpectBucketCount(
+        internal::kPageLoadPrerenderObserverEvent,
+        internal::PageLoadPrerenderObserverEvent::
+            kRecordNormalizedResponsivenessMetrics,
+        1);
+
     std::vector<std::string> ukm_list = {
         "InteractiveTiming.WorstUserInteractionLatency.MaxEventDuration",
         "InteractiveTiming.AverageUserInteractionLatencyOverBudget."
@@ -125,6 +131,10 @@ IN_PROC_BROWSER_TEST_F(PrerenderPageLoadMetricsObserverBrowserTest,
   GURL prerender_url = embedded_test_server()->GetURL("/title2.html");
   prerender_helper_.AddPrerender(prerender_url);
 
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kOnPrerenderStart, 1);
+
   // Activate and wait for FCP.
   auto waiter = std::make_unique<page_load_metrics::PageLoadMetricsTestWaiter>(
       web_contents());
@@ -133,18 +143,30 @@ IN_PROC_BROWSER_TEST_F(PrerenderPageLoadMetricsObserverBrowserTest,
   prerender_helper_.NavigatePrimaryPage(prerender_url);
   waiter->Wait();
 
-  // Expect only FP and FCP for prerender are recorded.
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kDidActivatePrerenderedPage, 1);
   histogram_tester().ExpectTotalCount(
       prerender_helper_.GenerateHistogramName(
           internal::kHistogramPrerenderNavigationToActivation,
           content::PrerenderTriggerType::kSpeculationRule, ""),
       1);
+
+  // Expect only FP and FCP for prerender are recorded.
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kOnFirstPaintInPage, 1);
   histogram_tester().ExpectTotalCount(
       prerender_helper_.GenerateHistogramName(
           internal::kHistogramPrerenderActivationToFirstPaint,
           content::PrerenderTriggerType::kSpeculationRule, ""),
       1);
   histogram_tester().ExpectTotalCount(internal::kHistogramFirstPaint, 0);
+
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kOnFirstContentfulPaintInPage,
+      1);
   histogram_tester().ExpectTotalCount(
       prerender_helper_.GenerateHistogramName(
           internal::kHistogramPrerenderActivationToFirstContentfulPaint,
@@ -161,6 +183,9 @@ IN_PROC_BROWSER_TEST_F(PrerenderPageLoadMetricsObserverBrowserTest,
   waiter->Wait();
 
   // Expect only FID for prerender is recorded.
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kOnFirstInputInPage, 1);
   histogram_tester().ExpectTotalCount(
       prerender_helper_.GenerateHistogramName(
           internal::kHistogramPrerenderFirstInputDelay4,
@@ -174,6 +199,12 @@ IN_PROC_BROWSER_TEST_F(PrerenderPageLoadMetricsObserverBrowserTest,
       ui_test_utils::NavigateToURL(browser(), GURL(url::kAboutBlankURL)));
 
   // Expect only LCP for prerender is recorded.
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kOnComplete, 1);
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kRecordSessionEndHistograms, 1);
   histogram_tester().ExpectTotalCount(
       prerender_helper_.GenerateHistogramName(
           internal::kHistogramPrerenderActivationToLargestContentfulPaint2,
@@ -182,6 +213,10 @@ IN_PROC_BROWSER_TEST_F(PrerenderPageLoadMetricsObserverBrowserTest,
   histogram_tester().ExpectTotalCount(
       internal::kHistogramLargestContentfulPaint, 0);
 
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kRecordLayoutShiftScoreMetrics,
+      1);
   histogram_tester().ExpectTotalCount(
       prerender_helper_.GenerateHistogramName(
           internal::kHistogramPrerenderCumulativeShiftScore,
@@ -270,6 +305,10 @@ IN_PROC_BROWSER_TEST_F(PrerenderPageLoadMetricsObserverBrowserTest,
   GURL prerender_url = embedded_test_server()->GetURL("/title2.html");
   prerender_helper_.AddPrerender(prerender_url);
 
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kOnPrerenderStart, 1);
+
   // Start an activation.
   prerender_helper_.NavigatePrimaryPage(prerender_url);
 
@@ -283,6 +322,13 @@ IN_PROC_BROWSER_TEST_F(PrerenderPageLoadMetricsObserverBrowserTest,
   ASSERT_TRUE(
       ui_test_utils::NavigateToURL(browser(), GURL(url::kAboutBlankURL)));
 
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kOnComplete, 1);
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kRecordSessionEndHistograms, 1);
+
   auto entries = GetMergedUkmEntries(PrerenderPageLoad::kEntryName);
   EXPECT_EQ(2u, entries.size());
 
@@ -335,6 +381,10 @@ IN_PROC_BROWSER_TEST_F(PrerenderPageLoadMetricsObserverBrowserTest,
   int host_id = prerender_helper_.GetHostForUrl(prerender_url);
   EXPECT_NE(host_id, content::RenderFrameHost::kNoFrameTreeNodeId);
 
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kOnPrerenderStart, 1);
+
   // Activate and wait for FCP.
   auto waiter = std::make_unique<page_load_metrics::PageLoadMetricsTestWaiter>(
       web_contents());
@@ -348,20 +398,32 @@ IN_PROC_BROWSER_TEST_F(PrerenderPageLoadMetricsObserverBrowserTest,
       /*is_renderer_initiated=*/false));
   waiter->Wait();
 
-  // Expect only FP and FCP for prerender are recorded.
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kDidActivatePrerenderedPage, 1);
   histogram_tester().ExpectTotalCount(
       prerender_helper_.GenerateHistogramName(
           internal::kHistogramPrerenderNavigationToActivation,
           content::PrerenderTriggerType::kEmbedder,
           prerender_utils::kDirectUrlInputMetricSuffix),
       1);
+
+  // Expect only FP and FCP for prerender are recorded.
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kOnFirstPaintInPage, 1);
   histogram_tester().ExpectTotalCount(
       prerender_helper_.GenerateHistogramName(
           internal::kHistogramPrerenderActivationToFirstPaint,
           content::PrerenderTriggerType::kEmbedder,
           prerender_utils::kDirectUrlInputMetricSuffix),
       1);
   histogram_tester().ExpectTotalCount(internal::kHistogramFirstPaint, 0);
+
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kOnFirstContentfulPaintInPage,
+      1);
   histogram_tester().ExpectTotalCount(
       prerender_helper_.GenerateHistogramName(
           internal::kHistogramPrerenderActivationToFirstContentfulPaint,
@@ -379,6 +441,9 @@ IN_PROC_BROWSER_TEST_F(PrerenderPageLoadMetricsObserverBrowserTest,
   waiter->Wait();
 
   // Expect only FID for prerender is recorded.
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kOnFirstInputInPage, 1);
   histogram_tester().ExpectTotalCount(
       prerender_helper_.GenerateHistogramName(
           internal::kHistogramPrerenderFirstInputDelay4,
@@ -393,6 +458,12 @@ IN_PROC_BROWSER_TEST_F(PrerenderPageLoadMetricsObserverBrowserTest,
       ui_test_utils::NavigateToURL(browser(), GURL(url::kAboutBlankURL)));
 
   // Expect only LCP for prerender is recorded.
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kOnComplete, 1);
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kRecordSessionEndHistograms, 1);
   histogram_tester().ExpectTotalCount(
       prerender_helper_.GenerateHistogramName(
           internal::kHistogramPrerenderActivationToLargestContentfulPaint2,
@@ -402,6 +473,10 @@ IN_PROC_BROWSER_TEST_F(PrerenderPageLoadMetricsObserverBrowserTest,
   histogram_tester().ExpectTotalCount(
       internal::kHistogramLargestContentfulPaint, 0);
 
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kRecordLayoutShiftScoreMetrics,
+      1);
   histogram_tester().ExpectTotalCount(
       prerender_helper_.GenerateHistogramName(
           internal::kHistogramPrerenderCumulativeShiftScore,
@@ -437,6 +512,10 @@ IN_PROC_BROWSER_TEST_F(PrerenderPageLoadMetricsObserverBrowserTest,
   GURL prerender_url = embedded_test_server()->GetURL("/title2.html");
   const int host_id = prerender_helper_.AddPrerender(prerender_url);
 
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kOnPrerenderStart, 1);
+
   content::test::PrerenderHostObserver observer(*web_contents(), host_id);
   prerender_helper_.CancelPrerenderedPage(host_id);
   observer.WaitForDestroyed();
@@ -446,6 +525,23 @@ IN_PROC_BROWSER_TEST_F(PrerenderPageLoadMetricsObserverBrowserTest,
   ASSERT_TRUE(
       ui_test_utils::NavigateToURL(browser(), GURL(url::kAboutBlankURL)));
 
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kDidActivatePrerenderedPage, 0);
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kOnFirstPaintInPage, 0);
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kOnFirstContentfulPaintInPage,
+      0);
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kOnComplete, 1);
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kRecordSessionEndHistograms, 1);
+
   // As the prerender was cancelled, no prerendering metrics are recorded.
   EXPECT_EQ(0u, histogram_tester()
                     .GetTotalCountsForPrefix("PageLoad.Clients.Prerender.")
@@ -475,6 +571,10 @@ IN_PROC_BROWSER_TEST_F(PrerenderPageLoadMetricsObserverBrowserTest,
                                                       redirected_url.spec());
   prerender_helper_.AddPrerender(prerender_url);
 
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kOnPrerenderStart, 1);
+
   // Activate and wait for FCP.
   auto waiter = std::make_unique<page_load_metrics::PageLoadMetricsTestWaiter>(
       web_contents());
@@ -483,12 +583,30 @@ IN_PROC_BROWSER_TEST_F(PrerenderPageLoadMetricsObserverBrowserTest,
   prerender_helper_.NavigatePrimaryPage(prerender_url);
   waiter->Wait();
 
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kDidActivatePrerenderedPage, 1);
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kOnFirstPaintInPage, 1);
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kOnFirstContentfulPaintInPage,
+      1);
+
   // Force navigation to another page, which should force logging of histograms
   // persisted at the end of the page load lifetime.
   ASSERT_TRUE(
       ui_test_utils::NavigateToURL(browser(), GURL(url::kAboutBlankURL)));
 
-  // Verify that UKM records the URL after the redirection.
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kOnComplete, 1);
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kRecordSessionEndHistograms, 1);
+
+  // Verify that UKM records the URL after the redirection, not the initial URL.
   auto entries = GetMergedUkmEntries(PrerenderPageLoad::kEntryName);
   ASSERT_FALSE(base::Contains(entries, prerender_url));
   const ukm::mojom::UkmEntry* prerendered_page_entry =
@@ -535,6 +653,10 @@ IN_PROC_BROWSER_TEST_F(PrerenderPageLoadMetricsObserverBrowserTest,
     registry_observer.WaitForTrigger(kPrerenderingUrl);
   }
 
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kOnPrerenderStart, 1);
+
   int host_id = prerender_helper_.GetHostForUrl(kPrerenderingUrl);
   content::test::PrerenderHostObserver prerender_observer(*web_contents(),
                                                           host_id);
@@ -551,14 +673,38 @@ IN_PROC_BROWSER_TEST_F(PrerenderPageLoadMetricsObserverBrowserTest,
   main_document_response.WaitForRequest();
   main_document_response.Send(kResponseWithNoStore);
   main_document_response.Done();
+
+  auto waiter = std::make_unique<page_load_metrics::PageLoadMetricsTestWaiter>(
+      web_contents());
+  waiter->AddPageExpectation(page_load_metrics::PageLoadMetricsTestWaiter::
+                                 TimingField::kFirstContentfulPaint);
   primary_page_manager.WaitForNavigationFinished();
   prerender_observer.WaitForActivation();
+  waiter->Wait();
+
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kDidActivatePrerenderedPage, 1);
 
   // Force navigation to another page, which should force logging of metrics
   // persisted at the end of the page load lifetime.
   ASSERT_TRUE(
       ui_test_utils::NavigateToURL(browser(), GURL(url::kAboutBlankURL)));
 
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kOnFirstPaintInPage, 1);
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kOnFirstContentfulPaintInPage,
+      1);
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kOnComplete, 1);
+  histogram_tester().ExpectBucketCount(
+      internal::kPageLoadPrerenderObserverEvent,
+      internal::PageLoadPrerenderObserverEvent::kRecordSessionEndHistograms, 1);
+
   auto entries = GetMergedUkmEntries(PrerenderPageLoad::kEntryName);
   EXPECT_EQ(2u, entries.size());
 
@@ -574,4 +720,8 @@ IN_PROC_BROWSER_TEST_F(PrerenderPageLoadMetricsObserverBrowserTest,
   ukm_recorder().ExpectEntryMetric(
       prerendered_page_entry,
       PrerenderPageLoad::kMainFrameResource_RequestHasNoStoreName, 1);
+
+  EXPECT_TRUE(ukm_recorder().EntryHasMetric(
+      prerendered_page_entry,
+      PrerenderPageLoad::kTiming_ActivationToLargestContentfulPaintName));
 }