Partial revert of Report navigation restart penalty to PLM

Reverts all of the PLM changes in
https://chromium-review.googlesource.com/c/chromium/src/+/1334944
and a partial revert of the previews code because of merge conflicts.

git checkout 967d3a9b \
  chrome/browser/page_load_metrics/page* \
  chrome/browser/page_load_metrics/metrics*

Bug: 874150
Change-Id: Ic943baa1c8945c3dd033de5890ba0d70b2efd5bc
Reviewed-on: https://chromium-review.googlesource.com/c/1355331Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Reviewed-by: Bryan McQuade <bmcquade@chromium.org>
Commit-Queue: Robert Ogden <robertogden@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612305}

chrome/browser/page_load_metrics/metrics_web_contents_observer.cc

@@ -685,20 +685,6 @@ void MetricsWebContentsObserver::OnTimingUpdated(
   }
 }
 
-bool MetricsWebContentsObserver::ReportNavigationRestartPenalty(
-    content::NavigationHandle* navigation_handle,
-    const base::TimeDelta mainframe_navigation_restart_penalty) {
-  DCHECK(!navigation_handle->HasCommitted());
-  auto it = provisional_loads_.find(navigation_handle);
-  if (it == provisional_loads_.end())
-    return false;
-
-  it->second->metrics_update_dispatcher()
-      ->ReportMainFrameNavigationRestartPenalty(
-          mainframe_navigation_restart_penalty);
-  return true;
-}
-
 void MetricsWebContentsObserver::UpdateTiming(
     mojom::PageLoadTimingPtr timing,
     mojom::PageLoadMetadataPtr metadata,

chrome/browser/page_load_metrics/metrics_web_contents_observer.h

@@ -154,18 +154,6 @@ class MetricsWebContentsObserver
       const std::vector<mojom::ResourceDataUpdatePtr>& resources,
       mojom::PageRenderDataPtr render_data);
 
-  // Used to report that a NavigationThrottle or other browser intervention
-  // canceled a navigation and replaced it with a new navigation.
-  // |mainframe_navigation_restart_penalty| will be applied across all relevant
-  // timing deltas within the page for the page load tracker corresponding to
-  // |navigation_handle|. Returns whether or not there was an applicable
-  // navigation to update. This must be called before commit. Note: This method
-  // should not be called from a WebContentsObserver's DidFinishNavigation or
-  // DidStartNavigation since this would cause a race condition.
-  bool ReportNavigationRestartPenalty(
-      content::NavigationHandle* navigation_handle,
-      const base::TimeDelta mainframe_navigation_restart_penalty);
-
   // Informs the observers of the currently committed load that the event
   // corresponding to |event_key| has occurred. This should not be called within
   // WebContentsObserver::DidFinishNavigation methods.

chrome/browser/page_load_metrics/metrics_web_contents_observer_unittest.cc

@@ -459,35 +459,6 @@ TEST_F(MetricsWebContentsObserverTest, SubFrame) {
   CheckNoErrorEvents();
 }
 
-TEST_F(MetricsWebContentsObserverTest, ReportNavigationRestartPenalty) {
-  mojom::PageLoadTiming timing;
-  page_load_metrics::InitPageLoadTimingForTest(&timing);
-  timing.navigation_start = base::Time::FromDoubleT(1);
-  timing.response_start = base::TimeDelta::FromMilliseconds(10);
-
-  std::unique_ptr<content::NavigationSimulator> navigation_simulator =
-      content::NavigationSimulator::CreateRendererInitiated(
-          GURL(kDefaultTestUrl), main_rfh());
-  navigation_simulator->Start();
-
-  const base::TimeDelta penalty = base::TimeDelta::FromMilliseconds(5);
-  observer()->ReportNavigationRestartPenalty(
-      navigation_simulator->GetNavigationHandle(), penalty);
-
-  navigation_simulator->Commit();
-  SimulateTimingUpdate(timing);
-
-  NavigateToUntrackedUrl();
-  CheckNoErrorEvents();
-
-  ASSERT_EQ(1, CountCompleteTimingReported());
-  mojom::PageLoadTimingPtr got_timing = complete_timings()[0].Clone();
-  // TODO(crbug.com/906718): Test all updated metrics.
-  EXPECT_EQ(got_timing->navigation_start, timing.navigation_start - penalty);
-  EXPECT_EQ(got_timing->response_start.value(),
-            timing.response_start.value() - penalty);
-}
-
 TEST_F(MetricsWebContentsObserverTest, SameDocumentNoTrigger) {
   mojom::PageLoadTiming timing;
   page_load_metrics::InitPageLoadTimingForTest(&timing);

chrome/browser/page_load_metrics/page_load_metrics_update_dispatcher.cc

@@ -261,34 +261,15 @@ class PageLoadTimingMerger {
       : target_(target) {}
 
   // Merge timing values from |new_page_load_timing| into the target
-  // PageLoadTiming, applying the |navigation_start_offset| to applicable
-  // metrics with respect to |is_main_frame|.
-  void MergeAndApplyOffset(base::TimeDelta navigation_start_offset,
-                           const mojom::PageLoadTiming& new_page_load_timing,
-                           bool is_main_frame) {
-    // TODO(crbug.com/906718): This approach is hard to maintain and likely to
-    // get stale over time.
+  // PageLoadTiming;
+  void Merge(base::TimeDelta navigation_start_offset,
+             const mojom::PageLoadTiming& new_page_load_timing,
+             bool is_main_frame) {
     MergePaintTiming(navigation_start_offset,
                      *new_page_load_timing.paint_timing, is_main_frame);
     MergeInteractiveTiming(navigation_start_offset,
                            *new_page_load_timing.interactive_timing,
                            is_main_frame);
-    // Don't need to merge these main-frame only metrics: merely apply the
-    // offset.
-    if (is_main_frame) {
-      target_->navigation_start =
-          new_page_load_timing.navigation_start + navigation_start_offset;
-      MaybeUpdateTimeDelta(&target_->response_start, navigation_start_offset,
-                           new_page_load_timing.response_start);
-      MaybeUpdateTimeDelta(&target_->input_to_navigation_start,
-                           navigation_start_offset,
-                           new_page_load_timing.input_to_navigation_start);
-
-      ApplyDocumentTimingOffset(navigation_start_offset,
-                                *new_page_load_timing.document_timing);
-      ApplyParseTimingOffset(navigation_start_offset,
-                             *new_page_load_timing.parse_timing);
-    }
   }
 
   // Whether we merged a new value.
@@ -362,25 +343,10 @@ class PageLoadTimingMerger {
     MaybeUpdateTimeDelta(&target_paint_timing->first_contentful_paint,
                          navigation_start_offset,
                          new_paint_timing.first_contentful_paint);
-    // These are currently a no-op on main frames.
-    MaybeUpdateTimeDelta(&target_paint_timing->largest_image_paint,
-                         navigation_start_offset,
-                         new_paint_timing.largest_image_paint);
-    MaybeUpdateTimeDelta(&target_paint_timing->last_image_paint,
-                         navigation_start_offset,
-                         new_paint_timing.last_image_paint);
-    MaybeUpdateTimeDelta(&target_paint_timing->largest_text_paint,
-                         navigation_start_offset,
-                         new_paint_timing.largest_text_paint);
-    MaybeUpdateTimeDelta(&target_paint_timing->last_text_paint,
-                         navigation_start_offset,
-                         new_paint_timing.last_text_paint);
-
     if (is_main_frame) {
       // First meaningful paint is only tracked in the main frame.
-      MaybeUpdateTimeDelta(&target_paint_timing->first_meaningful_paint,
-                           navigation_start_offset,
-                           new_paint_timing.first_meaningful_paint);
+      target_paint_timing->first_meaningful_paint =
+          new_paint_timing.first_meaningful_paint;
     }
   }
 
@@ -425,32 +391,6 @@ class PageLoadTimingMerger {
     }
   }
 
-  void ApplyDocumentTimingOffset(
-      base::TimeDelta navigation_start_offset,
-      const mojom::DocumentTiming& new_document_timing) {
-    mojom::DocumentTiming* target_document_timing =
-        target_->document_timing.get();
-    MaybeUpdateTimeDelta(
-        &target_document_timing->dom_content_loaded_event_start,
-        navigation_start_offset,
-        new_document_timing.dom_content_loaded_event_start);
-    MaybeUpdateTimeDelta(&target_document_timing->load_event_start,
-                         navigation_start_offset,
-                         new_document_timing.load_event_start);
-    MaybeUpdateTimeDelta(&target_document_timing->first_layout,
-                         navigation_start_offset,
-                         new_document_timing.first_layout);
-  }
-
-  void ApplyParseTimingOffset(base::TimeDelta navigation_start_offset,
-                              const mojom::ParseTiming& new_parse_timing) {
-    mojom::ParseTiming* target_parse_timing = target_->parse_timing.get();
-    MaybeUpdateTimeDelta(&target_parse_timing->parse_start,
-                         navigation_start_offset, new_parse_timing.parse_start);
-    MaybeUpdateTimeDelta(&target_parse_timing->parse_stop,
-                         navigation_start_offset, new_parse_timing.parse_stop);
-  }
-
   // The target PageLoadTiming we are merging values into.
   mojom::PageLoadTiming* const target_;
 
@@ -522,11 +462,6 @@ void PageLoadMetricsUpdateDispatcher::ShutDown() {
   }
 }
 
-void PageLoadMetricsUpdateDispatcher::ReportMainFrameNavigationRestartPenalty(
-    base::TimeDelta penalty) {
-  total_main_frame_navigation_restart_penalty_ += penalty;
-}
-
 void PageLoadMetricsUpdateDispatcher::UpdateMetrics(
     content::RenderFrameHost* render_frame_host,
     mojom::PageLoadTimingPtr new_timing,
@@ -600,13 +535,9 @@ void PageLoadMetricsUpdateDispatcher::UpdateSubFrameTiming(
 
   client_->OnSubFrameTimingChanged(render_frame_host, *new_timing);
 
-  // |total_main_frame_navigation_restart_penalty_| should also be applied to
-  // subframes since this penalty is associated with the main frame.
-  base::TimeDelta navigation_start_offset =
-      it->second - total_main_frame_navigation_restart_penalty_;
+  base::TimeDelta navigation_start_offset = it->second;
   PageLoadTimingMerger merger(pending_merged_page_timing_.get());
-  merger.MergeAndApplyOffset(navigation_start_offset, *new_timing,
-                             false /* is_main_frame */);
+  merger.Merge(navigation_start_offset, *new_timing, false /* is_main_frame */);
 
   MaybeDispatchTimingUpdates(merger.should_buffer_timing_update_callback());
 }
@@ -654,33 +585,9 @@ void PageLoadMetricsUpdateDispatcher::UpdateMainFrameTiming(
   mojom::InteractiveTimingPtr last_interactive_timing =
       std::move(pending_merged_page_timing_->interactive_timing);
 
-  base::TimeDelta navigation_start_offset =
-      -total_main_frame_navigation_restart_penalty_;
   // Update the latest candidate to the corresponding buffers. We will dispatch
   // the last candidate at the page load end. Because we don't want to dispatch
   // the non-last candidate here, we clear it from |new_timing|.
-  // Since this also means that these timings won't get
-  // |navigation_start_offset| applied in the merger, apply it here.
-  if (new_timing->paint_timing->largest_image_paint.has_value()) {
-    new_timing->paint_timing->largest_image_paint =
-        new_timing->paint_timing->largest_image_paint.value() +
-        navigation_start_offset;
-  }
-  if (new_timing->paint_timing->last_image_paint.has_value()) {
-    new_timing->paint_timing->last_image_paint =
-        new_timing->paint_timing->last_image_paint.value() +
-        navigation_start_offset;
-  }
-  if (new_timing->paint_timing->largest_text_paint.has_value()) {
-    new_timing->paint_timing->largest_text_paint =
-        new_timing->paint_timing->largest_text_paint.value() +
-        navigation_start_offset;
-  }
-  if (new_timing->paint_timing->last_text_paint.has_value()) {
-    new_timing->paint_timing->last_text_paint =
-        new_timing->paint_timing->last_text_paint.value() +
-        navigation_start_offset;
-  }
   largest_image_paint_.swap(new_timing->paint_timing->largest_image_paint);
   new_timing->paint_timing->largest_image_paint.reset();
   last_image_paint_.swap(new_timing->paint_timing->last_image_paint);
@@ -699,8 +606,7 @@ void PageLoadMetricsUpdateDispatcher::UpdateMainFrameTiming(
       std::move(last_interactive_timing);
 
   PageLoadTimingMerger merger(pending_merged_page_timing_.get());
-  merger.MergeAndApplyOffset(navigation_start_offset, *new_timing,
-                             true /* is_main_frame */);
+  merger.Merge(base::TimeDelta(), *new_timing, true /* is_main_frame */);
   MaybeDispatchTimingUpdates(merger.should_buffer_timing_update_callback());
 }
 

chrome/browser/page_load_metrics/page_load_metrics_update_dispatcher.h

@@ -136,11 +136,6 @@ class PageLoadMetricsUpdateDispatcher {
   void DidFinishSubFrameNavigation(
       content::NavigationHandle* navigation_handle);
 
-  // Increases |total_main_frame_navigation_restart_penalty_| by the given
-  // delta. This should be fully updated before commit. See the comment on
-  // |total_main_frame_navigation_restart_penalty_|.
-  void ReportMainFrameNavigationRestartPenalty(base::TimeDelta penalty);
-
   void ShutDown();
 
   const mojom::PageLoadTiming& timing() const {
@@ -204,13 +199,6 @@ class PageLoadMetricsUpdateDispatcher {
   mojom::PageLoadMetadataPtr subframe_metadata_;
 
   mojom::PageRenderDataPtr main_frame_render_data_;
-  // This time delta is an otherwise unknown penalty where the final navigation
-  // to a page was not the original (i.e.: user started) navigation. This can be
-  // caused by client redirects or other browser-based interventions like
-  // previews. Applying this delta will reconcile this page load metric with the
-  // time when the original navigation started. This will be applied to all
-  // metrics just before they are sent to the client.
-  base::TimeDelta total_main_frame_navigation_restart_penalty_;
 
   // Navigation start offsets for the most recently committed document in each
   // frame.

chrome/browser/previews/previews_lite_page_browsertest.cc

@@ -636,10 +636,6 @@ IN_PROC_BROWSER_TEST_F(PreviewsLitePageServerBrowserTest,
         1);
     histogram_tester.ExpectBucketCount("Previews.ServerLitePage.Triggered",
                                        false, 1);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.ReportedNavigationRestartPenalty", 0);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.NotReportedNavigationRestartPenalty", 0);
   }
 
   {
@@ -649,10 +645,6 @@ IN_PROC_BROWSER_TEST_F(PreviewsLitePageServerBrowserTest,
     VerifyPreviewLoaded();
     histogram_tester.ExpectBucketCount("Previews.ServerLitePage.Triggered",
                                        true, 1);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.ReportedNavigationRestartPenalty", 1);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.NotReportedNavigationRestartPenalty", 0);
   }
 
   {
@@ -668,10 +660,6 @@ IN_PROC_BROWSER_TEST_F(PreviewsLitePageServerBrowserTest,
         1);
     histogram_tester.ExpectBucketCount("Previews.ServerLitePage.Triggered",
                                        false, 1);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.ReportedNavigationRestartPenalty", 0);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.NotReportedNavigationRestartPenalty", 0);
   }
 
   {
@@ -693,10 +681,6 @@ IN_PROC_BROWSER_TEST_F(PreviewsLitePageServerBrowserTest,
         PreviewsLitePageNavigationThrottle::IneligibleReason::kHttpPost, 1);
     histogram_tester.ExpectBucketCount("Previews.ServerLitePage.Triggered",
                                        false, 1);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.ReportedNavigationRestartPenalty", 0);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.NotReportedNavigationRestartPenalty", 0);
   }
 
   {
@@ -712,10 +696,6 @@ IN_PROC_BROWSER_TEST_F(PreviewsLitePageServerBrowserTest,
         1);
     histogram_tester.ExpectBucketCount("Previews.ServerLitePage.Triggered",
                                        false, 1);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.ReportedNavigationRestartPenalty", 0);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.NotReportedNavigationRestartPenalty", 0);
   }
 
   {
@@ -729,10 +709,6 @@ IN_PROC_BROWSER_TEST_F(PreviewsLitePageServerBrowserTest,
         1);
     histogram_tester.ExpectBucketCount("Previews.ServerLitePage.Triggered",
                                        false, 1);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.ReportedNavigationRestartPenalty", 0);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.NotReportedNavigationRestartPenalty", 0);
     VerifyErrorPageLoaded();
   }
 
@@ -749,10 +725,6 @@ IN_PROC_BROWSER_TEST_F(PreviewsLitePageServerBrowserTest,
         1);
     histogram_tester.ExpectBucketCount("Previews.ServerLitePage.Triggered",
                                        false, 1);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.ReportedNavigationRestartPenalty", 0);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.NotReportedNavigationRestartPenalty", 0);
   }
 
   {
@@ -772,10 +744,6 @@ IN_PROC_BROWSER_TEST_F(PreviewsLitePageServerBrowserTest,
         1);
     histogram_tester.ExpectBucketCount("Previews.ServerLitePage.Triggered",
                                        false, 1);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.ReportedNavigationRestartPenalty", 0);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.NotReportedNavigationRestartPenalty", 0);
 
     // Reset ECT for future tests.
     g_browser_process->network_quality_tracker()
@@ -884,10 +852,6 @@ IN_PROC_BROWSER_TEST_F(PreviewsLitePageServerBrowserTest,
     ClearDeciderState();
     histogram_tester.ExpectBucketCount("Previews.ServerLitePage.Triggered",
                                        true, 1);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.ReportedNavigationRestartPenalty", 1);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.NotReportedNavigationRestartPenalty", 0);
     histogram_tester.ExpectTotalCount(
         "Previews.ServerLitePage.HttpOnlyFallbackPenalty", 1);
     histogram_tester.ExpectBucketCount(
@@ -907,10 +871,6 @@ IN_PROC_BROWSER_TEST_F(PreviewsLitePageServerBrowserTest,
 
     histogram_tester.ExpectBucketCount("Previews.ServerLitePage.Triggered",
                                        true, 1);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.ReportedNavigationRestartPenalty", 1);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.NotReportedNavigationRestartPenalty", 0);
     histogram_tester.ExpectTotalCount(
         "Previews.ServerLitePage.HttpOnlyFallbackPenalty", 1);
     histogram_tester.ExpectBucketCount(
@@ -940,10 +900,6 @@ IN_PROC_BROWSER_TEST_F(PreviewsLitePageServerBrowserTest,
     ClearDeciderState();
     histogram_tester.ExpectBucketCount("Previews.ServerLitePage.Triggered",
                                        true, 1);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.ReportedNavigationRestartPenalty", 2);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.NotReportedNavigationRestartPenalty", 0);
     histogram_tester.ExpectTotalCount(
         "Previews.ServerLitePage.HttpOnlyFallbackPenalty", 1);
     histogram_tester.ExpectBucketCount(
@@ -959,10 +915,6 @@ IN_PROC_BROWSER_TEST_F(PreviewsLitePageServerBrowserTest,
     ClearDeciderState();
     histogram_tester.ExpectBucketCount("Previews.ServerLitePage.Triggered",
                                        true, 1);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.ReportedNavigationRestartPenalty", 2);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.NotReportedNavigationRestartPenalty", 0);
     histogram_tester.ExpectTotalCount(
         "Previews.ServerLitePage.HttpOnlyFallbackPenalty", 1);
     histogram_tester.ExpectBucketCount(
@@ -1088,29 +1040,6 @@ IN_PROC_BROWSER_TEST_F(PreviewsLitePageServerTimeoutBrowserTest,
     histogram_tester.ExpectBucketCount(
         "Previews.ServerLitePage.ServerResponse",
         PreviewsLitePageNavigationThrottle::ServerResponse::kTimeout, 1);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.ReportedNavigationRestartPenalty", 2);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.NotReportedNavigationRestartPenalty", 0);
-    // Since this test already has a delay baked in, make sure the reported
-    // penalty is at least the length of the delay.
-    int max_penalty = 0;
-    for (const base::Bucket& bucket : histogram_tester.GetAllSamples(
-             "Previews.ServerLitePage.ReportedNavigationRestartPenalty")) {
-      if (bucket.min > max_penalty) {
-        max_penalty = bucket.min;
-      }
-    }
-    // Expecting |max_penalty| > |kTimeoutMs| is flaky in release builds because
-    // of histogram bucketing. Since HistogramTester::Bucket doesn't provide a
-    // bucket max, if |max_penalty| < |kTimeoutMs|, check that a sample exists
-    // in the |kTimeoutMs| bucket.
-    if (max_penalty <= kTimeoutMs) {
-      EXPECT_GE(histogram_tester.GetBucketCount(
-                    "Previews.ServerLitePage.ReportedNavigationRestartPenalty",
-                    kTimeoutMs),
-                1);
-    }  // else, test passes
   }
 
   {
@@ -1154,10 +1083,6 @@ IN_PROC_BROWSER_TEST_F(PreviewsLitePageServerBadServerBrowserTest,
 
     histogram_tester.ExpectBucketCount("Previews.ServerLitePage.Triggered",
                                        true, 1);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.ReportedNavigationRestartPenalty", 2);
-    histogram_tester.ExpectTotalCount(
-        "Previews.ServerLitePage.NotReportedNavigationRestartPenalty", 0);
     histogram_tester.ExpectBucketCount(
         "Previews.ServerLitePage.ServerResponse",
         PreviewsLitePageNavigationThrottle::ServerResponse::kFailed, 1);

chrome/browser/previews/previews_lite_page_navigation_throttle.cc

@@ -24,7 +24,6 @@
 #include "chrome/browser/content_settings/cookie_settings_factory.h"
 #include "chrome/browser/net/spdyproxy/data_reduction_proxy_chrome_settings.h"
 #include "chrome/browser/net/spdyproxy/data_reduction_proxy_chrome_settings_factory.h"
-#include "chrome/browser/page_load_metrics/metrics_web_contents_observer.h"
 #include "chrome/browser/previews/previews_lite_page_decider.h"
 #include "chrome/browser/previews/previews_service.h"
 #include "chrome/browser/previews/previews_service_factory.h"
@@ -93,43 +92,6 @@ content::OpenURLParams MakeOpenURLParams(content::NavigationHandle* handle,
   return url_params;
 }
 
-// This is called on |WillStartRequest| to check whether the given |handle| is
-// for a navigation that was started by this preview. If it was, the penalty
-// (time between the original navigation start and the navigation start of
-// |handle|) is reported to PLM.
-void MaybeReportNavigationRestartPenalty(content::NavigationHandle* handle) {
-  PreviewsUITabHelper* ui_tab_helper =
-      PreviewsUITabHelper::FromWebContents(handle->GetWebContents());
-  if (!ui_tab_helper)
-    return;
-
-  previews::PreviewsUserData* previews_data =
-      ui_tab_helper->GetPreviewsUserData(handle);
-  if (!previews_data)
-    return;
-
-  previews::PreviewsUserData::ServerLitePageInfo* info =
-      previews_data->server_lite_page_info();
-  if (!info)
-    return;
-
-  DCHECK_GT(info->original_navigation_start, base::TimeTicks());
-  base::TimeDelta penalty =
-      handle->NavigationStart() - info->original_navigation_start;
-
-  bool updated = page_load_metrics::MetricsWebContentsObserver::FromWebContents(
-                     handle->GetWebContents())
-                     ->ReportNavigationRestartPenalty(handle, penalty);
-  DCHECK(updated);
-  if (updated) {
-    UMA_HISTOGRAM_MEDIUM_TIMES(
-        "Previews.ServerLitePage.ReportedNavigationRestartPenalty", penalty);
-  } else {
-    UMA_HISTOGRAM_MEDIUM_TIMES(
-        "Previews.ServerLitePage.NotReportedNavigationRestartPenalty", penalty);
-  }
-}
-
 // Gets the ServerLitePageInfo struct from an existing attempted lite page
 // navigation, if there is one. If not, returns nullptr.
 std::unique_ptr<previews::PreviewsUserData::ServerLitePageInfo>
@@ -581,7 +543,6 @@ PreviewsLitePageNavigationThrottle::WillStartRequest() {
     return content::NavigationThrottle::CANCEL;
   }
 
-  MaybeReportNavigationRestartPenalty(navigation_handle());
   return MaybeNavigateToPreview();
 }