service worker: Add LCP metric, remove FMP.

We care more about LargestContentfulPaint than FirstMeaningfulPaint
these days.

Bug: 1119700
Change-Id: If9502b42366bd342f5c57e89960d86a17d2fa591
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2586174
Commit-Queue: Matt Falkenhagen <falken@chromium.org>
Reviewed-by: Charlie Harrison <csharrison@chromium.org>
Reviewed-by: Brian White <bcwhite@chromium.org>
Reviewed-by: Makoto Shimazu <shimazu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#836929}

chrome/browser/page_load_metrics/observers/service_worker_page_load_metrics_observer.cc

@@ -48,17 +48,14 @@ const char kBackgroundHistogramServiceWorkerFirstContentfulPaint[] =
 const char kHistogramServiceWorkerParseStartToFirstContentfulPaint[] =
     "PageLoad.Clients.ServiceWorker2.PaintTiming."
     "ParseStartToFirstContentfulPaint";
-const char kHistogramServiceWorkerFirstMeaningfulPaint[] =
-    "PageLoad.Clients.ServiceWorker2.Experimental.PaintTiming."
-    "NavigationToFirstMeaningfulPaint";
-const char kHistogramServiceWorkerParseStartToFirstMeaningfulPaint[] =
-    "PageLoad.Clients.ServiceWorker2.Experimental.PaintTiming."
-    "ParseStartToFirstMeaningfulPaint";
 const char kHistogramServiceWorkerDomContentLoaded[] =
     "PageLoad.Clients.ServiceWorker2.DocumentTiming."
     "NavigationToDOMContentLoadedEventFired";
 const char kHistogramServiceWorkerLoad[] =
     "PageLoad.Clients.ServiceWorker2.DocumentTiming.NavigationToLoadEventFired";
+const char kHistogramServiceWorkerLargestContentfulPaint[] =
+    "PageLoad.Clients.ServiceWorker2.PaintTiming."
+    "NavigationToLargestContentfulPaint2";
 
 const char kHistogramServiceWorkerParseStartInbox[] =
     "PageLoad.Clients.ServiceWorker2.ParseTiming.NavigationToParseStart.inbox";
@@ -68,12 +65,6 @@ const char kHistogramServiceWorkerFirstContentfulPaintInbox[] =
 const char kHistogramServiceWorkerParseStartToFirstContentfulPaintInbox[] =
     "PageLoad.Clients.ServiceWorker2.PaintTiming."
     "ParseStartToFirstContentfulPaint.inbox";
-const char kHistogramServiceWorkerFirstMeaningfulPaintInbox[] =
-    "PageLoad.Clients.ServiceWorker2.Experimental.PaintTiming."
-    "NavigationToFirstMeaningfulPaint.inbox";
-const char kHistogramServiceWorkerParseStartToFirstMeaningfulPaintInbox[] =
-    "PageLoad.Clients.ServiceWorker2.Experimental.PaintTiming."
-    "ParseStartToFirstMeaningfulPaint.inbox";
 const char kHistogramServiceWorkerDomContentLoadedInbox[] =
     "PageLoad.Clients.ServiceWorker2.DocumentTiming."
     "NavigationToDOMContentLoadedEventFired.inbox";
@@ -89,12 +80,6 @@ const char kHistogramServiceWorkerFirstContentfulPaintSearch[] =
 const char kHistogramServiceWorkerParseStartToFirstContentfulPaintSearch[] =
     "PageLoad.Clients.ServiceWorker2.PaintTiming."
     "ParseStartToFirstContentfulPaint.search";
-const char kHistogramServiceWorkerFirstMeaningfulPaintSearch[] =
-    "PageLoad.Clients.ServiceWorker2.Experimental.PaintTiming."
-    "NavigationToFirstMeaningfulPaint.search";
-const char kHistogramServiceWorkerParseStartToFirstMeaningfulPaintSearch[] =
-    "PageLoad.Clients.ServiceWorker2.Experimental.PaintTiming."
-    "ParseStartToFirstMeaningfulPaint.search";
 const char kHistogramServiceWorkerDomContentLoadedSearch[] =
     "PageLoad.Clients.ServiceWorker2.DocumentTiming."
     "NavigationToDOMContentLoadedEventFired.search";
@@ -108,12 +93,6 @@ const char kHistogramNoServiceWorkerFirstContentfulPaintSearch[] =
 const char kHistogramNoServiceWorkerParseStartToFirstContentfulPaintSearch[] =
     "PageLoad.Clients.NoServiceWorker2.PaintTiming."
     "ParseStartToFirstContentfulPaint.search";
-const char kHistogramNoServiceWorkerFirstMeaningfulPaintSearch[] =
-    "PageLoad.Clients.NoServiceWorker2.Experimental.PaintTiming."
-    "NavigationToFirstMeaningfulPaint.search";
-const char kHistogramNoServiceWorkerParseStartToFirstMeaningfulPaintSearch[] =
-    "PageLoad.Clients.NoServiceWorker2.Experimental.PaintTiming."
-    "ParseStartToFirstMeaningfulPaint.search";
 const char kHistogramNoServiceWorkerDomContentLoadedSearch[] =
     "PageLoad.Clients.NoServiceWorker2.DocumentTiming."
     "NavigationToDOMContentLoadedEventFired.search";
@@ -247,53 +226,6 @@ void ServiceWorkerPageLoadMetricsObserver::OnFirstContentfulPaintInPage(
   }
 }
 
-void ServiceWorkerPageLoadMetricsObserver::
-    OnFirstMeaningfulPaintInMainFrameDocument(
-        const page_load_metrics::mojom::PageLoadTiming& timing) {
-  if (!page_load_metrics::WasStartedInForegroundOptionalEventInForeground(
-          timing.paint_timing->first_meaningful_paint, GetDelegate())) {
-    return;
-  }
-  if (!IsServiceWorkerControlled()) {
-    if (!page_load_metrics::IsGoogleSearchResultUrl(GetDelegate().GetUrl()))
-      return;
-    PAGE_LOAD_HISTOGRAM(
-        internal::kHistogramNoServiceWorkerFirstMeaningfulPaintSearch,
-        timing.paint_timing->first_meaningful_paint.value());
-    PAGE_LOAD_HISTOGRAM(
-        internal::
-            kHistogramNoServiceWorkerParseStartToFirstMeaningfulPaintSearch,
-        timing.paint_timing->first_meaningful_paint.value() -
-            timing.parse_timing->parse_start.value());
-    return;
-  }
-  PAGE_LOAD_HISTOGRAM(internal::kHistogramServiceWorkerFirstMeaningfulPaint,
-                      timing.paint_timing->first_meaningful_paint.value());
-  PAGE_LOAD_HISTOGRAM(
-      internal::kHistogramServiceWorkerParseStartToFirstMeaningfulPaint,
-      timing.paint_timing->first_meaningful_paint.value() -
-          timing.parse_timing->parse_start.value());
-
-  if (IsInboxSite(GetDelegate().GetUrl())) {
-    PAGE_LOAD_HISTOGRAM(
-        internal::kHistogramServiceWorkerFirstMeaningfulPaintInbox,
-        timing.paint_timing->first_meaningful_paint.value());
-    PAGE_LOAD_HISTOGRAM(
-        internal::kHistogramServiceWorkerParseStartToFirstMeaningfulPaintInbox,
-        timing.paint_timing->first_meaningful_paint.value() -
-            timing.parse_timing->parse_start.value());
-  } else if (page_load_metrics::IsGoogleSearchResultUrl(
-                 GetDelegate().GetUrl())) {
-    PAGE_LOAD_HISTOGRAM(
-        internal::kHistogramServiceWorkerFirstMeaningfulPaintSearch,
-        timing.paint_timing->first_meaningful_paint.value());
-    PAGE_LOAD_HISTOGRAM(
-        internal::kHistogramServiceWorkerParseStartToFirstMeaningfulPaintSearch,
-        timing.paint_timing->first_meaningful_paint.value() -
-            timing.parse_timing->parse_start.value());
-  }
-}
-
 void ServiceWorkerPageLoadMetricsObserver::OnDomContentLoadedEventStart(
     const page_load_metrics::mojom::PageLoadTiming& timing) {
   if (!page_load_metrics::WasStartedInForegroundOptionalEventInForeground(
@@ -420,6 +352,37 @@ void ServiceWorkerPageLoadMetricsObserver::OnLoadingBehaviorObserved(
   logged_ukm_event_ = true;
 }
 
+void ServiceWorkerPageLoadMetricsObserver::OnComplete(
+    const page_load_metrics::mojom::PageLoadTiming& timing) {
+  RecordTimingHistograms();
+}
+
+page_load_metrics::PageLoadMetricsObserver::ObservePolicy
+ServiceWorkerPageLoadMetricsObserver::FlushMetricsOnAppEnterBackground(
+    const page_load_metrics::mojom::PageLoadTiming& timing) {
+  //  This follows UmaPageLoadMetricsObserver.
+  if (GetDelegate().DidCommit())
+    RecordTimingHistograms();
+  return STOP_OBSERVING;
+}
+
+void ServiceWorkerPageLoadMetricsObserver::RecordTimingHistograms() {
+  if (!IsServiceWorkerControlled())
+    return;
+
+  const page_load_metrics::ContentfulPaintTimingInfo&
+      all_frames_largest_contentful_paint =
+          GetDelegate()
+              .GetLargestContentfulPaintHandler()
+              .MergeMainFrameAndSubframes();
+  if (all_frames_largest_contentful_paint.ContainsValidTime() &&
+      WasStartedInForegroundOptionalEventInForeground(
+          all_frames_largest_contentful_paint.Time(), GetDelegate())) {
+    PAGE_LOAD_HISTOGRAM(internal::kHistogramServiceWorkerLargestContentfulPaint,
+                        all_frames_largest_contentful_paint.Time().value());
+  }
+}
+
 bool ServiceWorkerPageLoadMetricsObserver::IsServiceWorkerControlled() {
   return (GetDelegate().GetMainFrameMetadata().behavior_flags &
           blink::LoadingBehaviorFlag::

chrome/browser/page_load_metrics/observers/service_worker_page_load_metrics_observer.h

@@ -23,17 +23,13 @@ extern const char kHistogramServiceWorkerFirstContentfulPaintForwardBack[];
 extern const char
     kHistogramServiceWorkerFirstContentfulPaintForwardBackNoStore[];
 extern const char kHistogramServiceWorkerParseStartToFirstContentfulPaint[];
-extern const char kHistogramServiceWorkerFirstMeaningfulPaint[];
-extern const char kHistogramServiceWorkerParseStartToFirstMeaningfulPaint[];
 extern const char kHistogramServiceWorkerDomContentLoaded[];
 extern const char kHistogramServiceWorkerLoad[];
+extern const char kHistogramServiceWorkerLargestContentfulPaint[];
 
 extern const char kHistogramServiceWorkerParseStartInbox[];
 extern const char kHistogramServiceWorkerFirstContentfulPaintInbox[];
 extern const char kHistogramServiceWorkerFirstInputDelay[];
-extern const char kHistogramServiceWorkerFirstMeaningfulPaintInbox[];
-extern const char
-    kHistogramServiceWorkerParseStartToFirstMeaningfulPaintInbox[];
 extern const char
     kHistogramServiceWorkerParseStartToFirstContentfulPaintInbox[];
 extern const char kHistogramServiceWorkerDomContentLoadedInbox[];
@@ -41,18 +37,12 @@ extern const char kHistogramServiceWorkerLoadInbox[];
 
 extern const char kHistogramServiceWorkerParseStartSearch[];
 extern const char kHistogramServiceWorkerFirstContentfulPaintSearch[];
-extern const char kHistogramServiceWorkerFirstMeaningfulPaintSearch[];
-extern const char
-    kHistogramServiceWorkerParseStartToFirstMeaningfulPaintSearch[];
 extern const char
     kHistogramServiceWorkerParseStartToFirstContentfulPaintSearch[];
 extern const char kHistogramServiceWorkerDomContentLoadedSearch[];
 extern const char kHistogramServiceWorkerLoadSearch[];
 
 extern const char kHistogramNoServiceWorkerFirstContentfulPaintSearch[];
-extern const char kHistogramNoServiceWorkerFirstMeaningfulPaintSearch[];
-extern const char
-    kHistogramNoServiceWorkerParseStartToFirstMeaningfulPaintSearch[];
 extern const char
     kHistogramNoServiceWorkerParseStartToFirstContentfulPaintSearch[];
 extern const char kHistogramNoServiceWorkerDomContentLoadedSearch[];
@@ -78,16 +68,20 @@ class ServiceWorkerPageLoadMetricsObserver
       const page_load_metrics::mojom::PageLoadTiming& timing) override;
   void OnFirstContentfulPaintInPage(
       const page_load_metrics::mojom::PageLoadTiming& timing) override;
-  void OnFirstMeaningfulPaintInMainFrameDocument(
-      const page_load_metrics::mojom::PageLoadTiming& timing) override;
   void OnDomContentLoadedEventStart(
       const page_load_metrics::mojom::PageLoadTiming& timing) override;
   void OnLoadEventStart(
       const page_load_metrics::mojom::PageLoadTiming& timing) override;
   void OnLoadingBehaviorObserved(content::RenderFrameHost* rfh,
                                  int behavior_flags) override;
+  void OnComplete(
+      const page_load_metrics::mojom::PageLoadTiming& timing) override;
+  page_load_metrics::PageLoadMetricsObserver::ObservePolicy
+  FlushMetricsOnAppEnterBackground(
+      const page_load_metrics::mojom::PageLoadTiming& timing) override;
 
  private:
+  void RecordTimingHistograms();
   bool IsServiceWorkerControlled();
 
   ui::PageTransition transition_ = ui::PAGE_TRANSITION_LINK;

chrome/browser/page_load_metrics/observers/service_worker_page_load_metrics_observer_unittest.cc

@@ -11,6 +11,7 @@
 #include "components/page_load_metrics/common/test/page_load_metrics_test_util.h"
 #include "content/public/browser/web_contents.h"
 #include "services/metrics/public/cpp/ukm_builders.h"
+#include "testing/gmock/include/gmock/gmock-matchers.h"
 
 namespace {
 
@@ -51,10 +52,6 @@ class ServiceWorkerPageLoadMetricsObserverTest
         0);
     tester()->histogram_tester().ExpectTotalCount(
         internal::kHistogramServiceWorkerParseStartToFirstContentfulPaint, 0);
-    tester()->histogram_tester().ExpectTotalCount(
-        internal::kHistogramServiceWorkerFirstMeaningfulPaint, 0);
-    tester()->histogram_tester().ExpectTotalCount(
-        internal::kHistogramServiceWorkerParseStartToFirstMeaningfulPaint, 0);
     tester()->histogram_tester().ExpectTotalCount(
         internal::kHistogramServiceWorkerDomContentLoaded, 0);
     tester()->histogram_tester().ExpectTotalCount(
@@ -63,6 +60,11 @@ class ServiceWorkerPageLoadMetricsObserverTest
         internal::kHistogramServiceWorkerParseStart, 0);
     tester()->histogram_tester().ExpectTotalCount(
         internal::kBackgroundHistogramServiceWorkerParseStart, 0);
+    tester()->histogram_tester().ExpectTotalCount(
+        internal::kHistogramServiceWorkerLargestContentfulPaint, 0);
+
+    tester()->histogram_tester().ExpectTotalCount(
+        internal::kHistogramServiceWorkerLargestContentfulPaint, 0);
   }
 
   void AssertNoInboxHistogramsLogged() {
@@ -73,11 +75,6 @@ class ServiceWorkerPageLoadMetricsObserverTest
     tester()->histogram_tester().ExpectTotalCount(
         internal::kHistogramServiceWorkerParseStartToFirstContentfulPaintInbox,
         0);
-    tester()->histogram_tester().ExpectTotalCount(
-        internal::kHistogramServiceWorkerFirstMeaningfulPaintInbox, 0);
-    tester()->histogram_tester().ExpectTotalCount(
-        internal::kHistogramServiceWorkerParseStartToFirstMeaningfulPaintInbox,
-        0);
     tester()->histogram_tester().ExpectTotalCount(
         internal::kHistogramServiceWorkerDomContentLoadedInbox, 0);
     tester()->histogram_tester().ExpectTotalCount(
@@ -92,11 +89,6 @@ class ServiceWorkerPageLoadMetricsObserverTest
     tester()->histogram_tester().ExpectTotalCount(
         internal::kHistogramServiceWorkerParseStartToFirstContentfulPaintSearch,
         0);
-    tester()->histogram_tester().ExpectTotalCount(
-        internal::kHistogramServiceWorkerFirstMeaningfulPaintSearch, 0);
-    tester()->histogram_tester().ExpectTotalCount(
-        internal::kHistogramServiceWorkerParseStartToFirstMeaningfulPaintSearch,
-        0);
     tester()->histogram_tester().ExpectTotalCount(
         internal::kHistogramServiceWorkerDomContentLoadedSearch, 0);
     tester()->histogram_tester().ExpectTotalCount(
@@ -110,12 +102,6 @@ class ServiceWorkerPageLoadMetricsObserverTest
         internal::
             kHistogramNoServiceWorkerParseStartToFirstContentfulPaintSearch,
         0);
-    tester()->histogram_tester().ExpectTotalCount(
-        internal::kHistogramNoServiceWorkerFirstMeaningfulPaintSearch, 0);
-    tester()->histogram_tester().ExpectTotalCount(
-        internal::
-            kHistogramNoServiceWorkerParseStartToFirstMeaningfulPaintSearch,
-        0);
     tester()->histogram_tester().ExpectTotalCount(
         internal::kHistogramNoServiceWorkerDomContentLoadedSearch, 0);
     tester()->histogram_tester().ExpectTotalCount(
@@ -134,12 +120,16 @@ class ServiceWorkerPageLoadMetricsObserverTest
     timing->paint_timing->first_paint = base::TimeDelta::FromMilliseconds(200);
     timing->paint_timing->first_contentful_paint =
         base::TimeDelta::FromMilliseconds(300);
-    timing->paint_timing->first_meaningful_paint =
-        base::TimeDelta::FromMilliseconds(700);
     timing->document_timing->dom_content_loaded_event_start =
         base::TimeDelta::FromMilliseconds(600);
     timing->document_timing->load_event_start =
         base::TimeDelta::FromMilliseconds(1000);
+
+    timing->paint_timing->largest_contentful_paint->largest_image_paint =
+        base::TimeDelta::FromMilliseconds(4780);
+    timing->paint_timing->largest_contentful_paint->largest_image_paint_size =
+        100u;
+
     PopulateRequiredTimingFields(timing);
   }
 };
@@ -178,11 +168,14 @@ TEST_F(ServiceWorkerPageLoadMetricsObserverTest, WithServiceWorker) {
   InitializeTestPageLoadTiming(&timing);
 
   NavigateAndCommit(GURL(kDefaultTestUrl));
+
   page_load_metrics::mojom::FrameMetadata metadata;
   metadata.behavior_flags |=
       blink::LoadingBehaviorFlag::kLoadingBehaviorServiceWorkerControlled;
   tester()->SimulateTimingAndMetadataUpdate(timing, metadata);
 
+  tester()->NavigateToUntrackedUrl();
+
   tester()->histogram_tester().ExpectTotalCount(
       internal::kHistogramServiceWorkerFirstInputDelay, 1);
   tester()->histogram_tester().ExpectBucketCount(
@@ -237,6 +230,10 @@ TEST_F(ServiceWorkerPageLoadMetricsObserverTest, WithServiceWorker) {
   tester()->histogram_tester().ExpectTotalCount(
       internal::kHistogramServiceWorkerParseStartForwardBackNoStore, 0);
 
+  EXPECT_THAT(tester()->histogram_tester().GetAllSamples(
+                  internal::kHistogramServiceWorkerLargestContentfulPaint),
+              testing::ElementsAre(base::Bucket(4780, 1)));
+
   const auto& entries = tester()->test_ukm_recorder().GetEntriesByName(
       ukm::builders::PageLoad_ServiceWorkerControlled::kEntryName);
   EXPECT_EQ(1u, entries.size());
@@ -262,7 +259,7 @@ TEST_F(ServiceWorkerPageLoadMetricsObserverTest, WithServiceWorkerBackground) {
   NavigateAndCommit(GURL(kDefaultTestUrl));
   tester()->SimulateTimingAndMetadataUpdate(timing, metadata);
 
-  // Background the tab, then forground it.
+  // Background the tab, then foreground it.
   web_contents()->WasHidden();
   web_contents()->WasShown();
 
@@ -280,14 +277,12 @@ TEST_F(ServiceWorkerPageLoadMetricsObserverTest, WithServiceWorkerBackground) {
       timing.paint_timing->first_contentful_paint.value().InMilliseconds(), 1);
   tester()->histogram_tester().ExpectTotalCount(
       internal::kHistogramServiceWorkerParseStartToFirstContentfulPaint, 0);
-  tester()->histogram_tester().ExpectTotalCount(
-      internal::kHistogramServiceWorkerFirstMeaningfulPaint, 0);
-  tester()->histogram_tester().ExpectTotalCount(
-      internal::kHistogramServiceWorkerParseStartToFirstMeaningfulPaint, 0);
   tester()->histogram_tester().ExpectTotalCount(
       internal::kHistogramServiceWorkerDomContentLoaded, 0);
   tester()->histogram_tester().ExpectTotalCount(
       internal::kHistogramServiceWorkerLoad, 0);
+  tester()->histogram_tester().ExpectTotalCount(
+      internal::kHistogramServiceWorkerLargestContentfulPaint, 0);
   // TODO(crbug.com/686590): The following expectation fails on Win7 Tests
   // (dbg)(1) builder, so is disabled for the time being.
   // tester()->histogram_tester().ExpectTotalCount(
@@ -365,35 +360,6 @@ TEST_F(ServiceWorkerPageLoadMetricsObserverTest, InboxSite) {
           .InMilliseconds(),
       1);
 
-  tester()->histogram_tester().ExpectTotalCount(
-      internal::kHistogramServiceWorkerFirstMeaningfulPaint, 1);
-  tester()->histogram_tester().ExpectBucketCount(
-      internal::kHistogramServiceWorkerFirstMeaningfulPaint,
-      timing.paint_timing->first_meaningful_paint.value().InMilliseconds(), 1);
-  tester()->histogram_tester().ExpectTotalCount(
-      internal::kHistogramServiceWorkerFirstMeaningfulPaintInbox, 1);
-  tester()->histogram_tester().ExpectBucketCount(
-      internal::kHistogramServiceWorkerFirstMeaningfulPaintInbox,
-      timing.paint_timing->first_meaningful_paint.value().InMilliseconds(), 1);
-
-  tester()->histogram_tester().ExpectTotalCount(
-      internal::kHistogramServiceWorkerParseStartToFirstMeaningfulPaint, 1);
-  tester()->histogram_tester().ExpectBucketCount(
-      internal::kHistogramServiceWorkerParseStartToFirstMeaningfulPaint,
-      (timing.paint_timing->first_meaningful_paint.value() -
-       timing.parse_timing->parse_start.value())
-          .InMilliseconds(),
-      1);
-  tester()->histogram_tester().ExpectTotalCount(
-      internal::kHistogramServiceWorkerParseStartToFirstMeaningfulPaintInbox,
-      1);
-  tester()->histogram_tester().ExpectBucketCount(
-      internal::kHistogramServiceWorkerParseStartToFirstMeaningfulPaintInbox,
-      (timing.paint_timing->first_meaningful_paint.value() -
-       timing.parse_timing->parse_start.value())
-          .InMilliseconds(),
-      1);
-
   tester()->histogram_tester().ExpectTotalCount(
       internal::kHistogramServiceWorkerDomContentLoaded, 1);
   tester()->histogram_tester().ExpectBucketCount(
@@ -488,35 +454,6 @@ TEST_F(ServiceWorkerPageLoadMetricsObserverTest, SearchSite) {
           .InMilliseconds(),
       1);
 
-  tester()->histogram_tester().ExpectTotalCount(
-      internal::kHistogramServiceWorkerFirstMeaningfulPaint, 1);
-  tester()->histogram_tester().ExpectBucketCount(
-      internal::kHistogramServiceWorkerFirstMeaningfulPaint,
-      timing.paint_timing->first_meaningful_paint.value().InMilliseconds(), 1);
-  tester()->histogram_tester().ExpectTotalCount(
-      internal::kHistogramServiceWorkerFirstMeaningfulPaintSearch, 1);
-  tester()->histogram_tester().ExpectBucketCount(
-      internal::kHistogramServiceWorkerFirstMeaningfulPaintSearch,
-      timing.paint_timing->first_meaningful_paint.value().InMilliseconds(), 1);
-
-  tester()->histogram_tester().ExpectTotalCount(
-      internal::kHistogramServiceWorkerParseStartToFirstMeaningfulPaint, 1);
-  tester()->histogram_tester().ExpectBucketCount(
-      internal::kHistogramServiceWorkerParseStartToFirstMeaningfulPaint,
-      (timing.paint_timing->first_meaningful_paint.value() -
-       timing.parse_timing->parse_start.value())
-          .InMilliseconds(),
-      1);
-  tester()->histogram_tester().ExpectTotalCount(
-      internal::kHistogramServiceWorkerParseStartToFirstMeaningfulPaintSearch,
-      1);
-  tester()->histogram_tester().ExpectBucketCount(
-      internal::kHistogramServiceWorkerParseStartToFirstMeaningfulPaintSearch,
-      (timing.paint_timing->first_meaningful_paint.value() -
-       timing.parse_timing->parse_start.value())
-          .InMilliseconds(),
-      1);
-
   tester()->histogram_tester().ExpectTotalCount(
       internal::kHistogramServiceWorkerDomContentLoaded, 1);
   tester()->histogram_tester().ExpectBucketCount(
@@ -576,22 +513,6 @@ TEST_F(ServiceWorkerPageLoadMetricsObserverTest, SearchNoSWSite) {
           .InMilliseconds(),
       1);
 
-  tester()->histogram_tester().ExpectTotalCount(
-      internal::kHistogramNoServiceWorkerFirstMeaningfulPaintSearch, 1);
-  tester()->histogram_tester().ExpectBucketCount(
-      internal::kHistogramNoServiceWorkerFirstMeaningfulPaintSearch,
-      timing.paint_timing->first_meaningful_paint.value().InMilliseconds(), 1);
-
-  tester()->histogram_tester().ExpectTotalCount(
-      internal::kHistogramNoServiceWorkerParseStartToFirstMeaningfulPaintSearch,
-      1);
-  tester()->histogram_tester().ExpectBucketCount(
-      internal::kHistogramNoServiceWorkerParseStartToFirstMeaningfulPaintSearch,
-      (timing.paint_timing->first_meaningful_paint.value() -
-       timing.parse_timing->parse_start.value())
-          .InMilliseconds(),
-      1);
-
   tester()->histogram_tester().ExpectTotalCount(
       internal::kHistogramNoServiceWorkerDomContentLoadedSearch, 1);
   tester()->histogram_tester().ExpectBucketCount(
@@ -628,6 +549,7 @@ TEST_F(ServiceWorkerPageLoadMetricsObserverTest,
   metadata.behavior_flags |=
       blink::LoadingBehaviorFlag::kLoadingBehaviorServiceWorkerControlled;
   tester()->SimulateTimingAndMetadataUpdate(timing, metadata);
+  tester()->NavigateToUntrackedUrl();
 
   tester()->histogram_tester().ExpectTotalCount(
       internal::kHistogramServiceWorkerFirstPaint, 1);
@@ -656,4 +578,46 @@ TEST_F(ServiceWorkerPageLoadMetricsObserverTest,
   tester()->histogram_tester().ExpectBucketCount(
       internal::kHistogramServiceWorkerParseStartForwardBack,
       timing.parse_timing->parse_start.value().InMilliseconds(), 1);
+
+  EXPECT_THAT(tester()->histogram_tester().GetAllSamples(
+                  internal::kHistogramServiceWorkerLargestContentfulPaint),
+              testing::ElementsAre(base::Bucket(4780, 1)));
+}
+
+TEST_F(ServiceWorkerPageLoadMetricsObserverTest,
+       FlushMetricsOnAppEnterBackground) {
+  page_load_metrics::mojom::PageLoadTiming timing;
+  InitializeTestPageLoadTiming(&timing);
+
+  NavigateAndCommit(GURL(kDefaultTestUrl));
+
+  page_load_metrics::mojom::FrameMetadata metadata;
+  metadata.behavior_flags |=
+      blink::LoadingBehaviorFlag::kLoadingBehaviorServiceWorkerControlled;
+  tester()->SimulateTimingAndMetadataUpdate(timing, metadata);
+
+  // Most timings have been recorded. Just test FCP for simplicity. LCP has not
+  // yet been recorded.
+  tester()->histogram_tester().ExpectTotalCount(
+      internal::kHistogramServiceWorkerFirstContentfulPaint, 1);
+  tester()->histogram_tester().ExpectBucketCount(
+      internal::kHistogramServiceWorkerFirstContentfulPaint,
+      timing.paint_timing->first_contentful_paint.value().InMilliseconds(), 1);
+  tester()->histogram_tester().ExpectTotalCount(
+      internal::kHistogramServiceWorkerLargestContentfulPaint, 0);
+
+  // This flushes LCP.
+  tester()->SimulateAppEnterBackground();
+  EXPECT_THAT(tester()->histogram_tester().GetAllSamples(
+                  internal::kHistogramServiceWorkerLargestContentfulPaint),
+              testing::ElementsAre(base::Bucket(4780, 1)));
+
+  // Navigate again, forcing completion callbacks to be called.
+  tester()->NavigateToUntrackedUrl();
+
+  // LCP will not be recorded again, since FlushMetricsOnAppEnterBackground()
+  // returned STOP_OBSERVING.
+  EXPECT_THAT(tester()->histogram_tester().GetAllSamples(
+                  internal::kHistogramServiceWorkerLargestContentfulPaint),
+              testing::ElementsAre(base::Bucket(4780, 1)));
 }

tools/metrics/histograms/histograms_xml/histogram_suffixes_list.xml

@@ -12780,9 +12780,17 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
   <affected-histogram
       name="PageLoad.Clients.NoServiceWorker.DocumentTiming.NavigationToLoadEventFired"/>
   <affected-histogram
-      name="PageLoad.Clients.NoServiceWorker.Experimental.PaintTiming.NavigationToFirstMeaningfulPaint"/>
+      name="PageLoad.Clients.NoServiceWorker.Experimental.PaintTiming.NavigationToFirstMeaningfulPaint">
+    <obsolete>
+      Removed in December 2020.
+    </obsolete>
+  </affected-histogram>
   <affected-histogram
-      name="PageLoad.Clients.NoServiceWorker.Experimental.PaintTiming.ParseStartToFirstMeaningfulPaint"/>
+      name="PageLoad.Clients.NoServiceWorker.Experimental.PaintTiming.ParseStartToFirstMeaningfulPaint">
+    <obsolete>
+      Removed in December 2020.
+    </obsolete>
+  </affected-histogram>
   <affected-histogram
       name="PageLoad.Clients.NoServiceWorker.PaintTiming.NavigationToFirstContentfulPaint"/>
   <affected-histogram
@@ -12956,15 +12964,25 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
   <affected-histogram
       name="PageLoad.DocumentTiming.NavigationToLoadEventFired"/>
   <affected-histogram
-      name="PageLoad.Experimental.PaintTiming.NavigationToFirstMeaningfulPaint"/>
+      name="PageLoad.Experimental.PaintTiming.NavigationToFirstMeaningfulPaint">
+    <obsolete>
+      Removed Dec 2020.
+    </obsolete>
+  </affected-histogram>
   <affected-histogram
-      name="PageLoad.Experimental.PaintTiming.ParseStartToFirstMeaningfulPaint"/>
+      name="PageLoad.Experimental.PaintTiming.ParseStartToFirstMeaningfulPaint">
+    <obsolete>
+      Removed Dec 2020.
+    </obsolete>
+  </affected-histogram>
   <affected-histogram name="PageLoad.InteractiveTiming.FirstInputDelay"/>
   <affected-histogram name="PageLoad.InteractiveTiming.FirstInputDelay2"/>
   <affected-histogram name="PageLoad.InteractiveTiming.FirstInputDelay3"/>
   <affected-histogram
       name="PageLoad.PaintTiming.NavigationToFirstContentfulPaint"/>
   <affected-histogram name="PageLoad.PaintTiming.NavigationToFirstPaint"/>
+  <affected-histogram
+      name="PageLoad.PaintTiming.NavigationToLargestContentfulPaint2"/>
   <affected-histogram
       name="PageLoad.PaintTiming.ParseStartToFirstContentfulPaint"/>
   <affected-histogram name="PageLoad.ParseTiming.NavigationToParseStart"/>
@@ -12986,9 +13004,17 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
   <affected-histogram
       name="PageLoad.Clients.ServiceWorker.DocumentTiming.NavigationToLoadEventFired"/>
   <affected-histogram
-      name="PageLoad.Clients.ServiceWorker.Experimental.PaintTiming.NavigationToFirstMeaningfulPaint"/>
+      name="PageLoad.Clients.ServiceWorker.Experimental.PaintTiming.NavigationToFirstMeaningfulPaint">
+    <obsolete>
+      Removed in December 2020.
+    </obsolete>
+  </affected-histogram>
   <affected-histogram
-      name="PageLoad.Clients.ServiceWorker.Experimental.PaintTiming.ParseStartToFirstMeaningfulPaint"/>
+      name="PageLoad.Clients.ServiceWorker.Experimental.PaintTiming.ParseStartToFirstMeaningfulPaint">
+    <obsolete>
+      Removed in December 2020.
+    </obsolete>
+  </affected-histogram>
   <affected-histogram
       name="PageLoad.Clients.ServiceWorker.PaintTiming.NavigationToFirstContentfulPaint"/>
   <affected-histogram
@@ -13000,9 +13026,17 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
   <affected-histogram
       name="PageLoad.Clients.ServiceWorker2.DocumentTiming.NavigationToLoadEventFired"/>
   <affected-histogram
-      name="PageLoad.Clients.ServiceWorker2.Experimental.PaintTiming.NavigationToFirstMeaningfulPaint"/>
+      name="PageLoad.Clients.ServiceWorker2.Experimental.PaintTiming.NavigationToFirstMeaningfulPaint">
+    <obsolete>
+      Removed in December 2020.
+    </obsolete>
+  </affected-histogram>
   <affected-histogram
-      name="PageLoad.Clients.ServiceWorker2.Experimental.PaintTiming.ParseStartToFirstMeaningfulPaint"/>
+      name="PageLoad.Clients.ServiceWorker2.Experimental.PaintTiming.ParseStartToFirstMeaningfulPaint">
+    <obsolete>
+      Removed in December 2020.
+    </obsolete>
+  </affected-histogram>
   <affected-histogram
       name="PageLoad.Clients.ServiceWorker2.PaintTiming.NavigationToFirstContentfulPaint"/>
   <affected-histogram