Update OnCommit to return ObservePolicy.

chrome/browser/page_load_metrics/observers/previews_page_load_metrics_observer.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/page_load_metrics/observers/previews_page_load_metrics_observer.h"
 
 #include <string>
 
 #include "base/optional.h"
 #include "base/time/time.h"
@@ skipping 21 matching lines @@
     "PageLoad.Clients.Previews.OfflinePages.DocumentTiming."
     "NavigationToLoadEventFired";
 const char kHistogramOfflinePreviewsFirstContentfulPaint[] =
     "PageLoad.Clients.Previews.OfflinePages.PaintTiming."
     "NavigationToFirstContentfulPaint";
 const char kHistogramOfflinePreviewsParseStart[] =
     "PageLoad.Clients.Previews.OfflinePages.ParseTiming.NavigationToParseStart";
 
 }  // namespace internal
 
-PreviewsPageLoadMetricsObserver::PreviewsPageLoadMetricsObserver()
-    : is_offline_preview_(false) {}
+PreviewsPageLoadMetricsObserver::PreviewsPageLoadMetricsObserver() {}
 
 PreviewsPageLoadMetricsObserver::~PreviewsPageLoadMetricsObserver() {}
 
-void PreviewsPageLoadMetricsObserver::OnCommit(
+page_load_metrics::PageLoadMetricsObserver::ObservePolicy
+PreviewsPageLoadMetricsObserver::OnCommit(
     content::NavigationHandle* navigation_handle) {
-  is_offline_preview_ = IsOfflinePreview(navigation_handle->GetWebContents());
+  return IsOfflinePreview(navigation_handle->GetWebContents())
+             ? CONTINUE_OBSERVING
+             : STOP_OBSERVING;
 }
 
 void PreviewsPageLoadMetricsObserver::OnDomContentLoadedEventStart(
     const page_load_metrics::PageLoadTiming& timing,
     const page_load_metrics::PageLoadExtraInfo& info) {
-  if (!is_offline_preview_ ||
-      !WasStartedInForegroundOptionalEventInForeground(
+  if (!WasStartedInForegroundOptionalEventInForeground(
           timing.dom_content_loaded_event_start, info)) {
     return;
   }
   PAGE_LOAD_HISTOGRAM(
       internal::kHistogramOfflinePreviewsDOMContentLoadedEventFired,
       timing.dom_content_loaded_event_start.value());
 }
 
 void PreviewsPageLoadMetricsObserver::OnLoadEventStart(
     const page_load_metrics::PageLoadTiming& timing,
     const page_load_metrics::PageLoadExtraInfo& info) {
-  if (!is_offline_preview_ ||
-      !WasStartedInForegroundOptionalEventInForeground(
+  if (!WasStartedInForegroundOptionalEventInForeground(
           timing.dom_content_loaded_event_start, info)) {
     return;
   }
   PAGE_LOAD_HISTOGRAM(internal::kHistogramOfflinePreviewsLoadEventFired,
                       timing.load_event_start.value());
 }
 
 void PreviewsPageLoadMetricsObserver::OnFirstLayout(
     const page_load_metrics::PageLoadTiming& timing,
     const page_load_metrics::PageLoadExtraInfo& info) {
-  if (!is_offline_preview_ ||
-      !WasStartedInForegroundOptionalEventInForeground(
+  if (!WasStartedInForegroundOptionalEventInForeground(
           timing.dom_content_loaded_event_start, info)) {
     return;
   }
   PAGE_LOAD_HISTOGRAM(internal::kHistogramOfflinePreviewsFirstLayout,
                       timing.first_layout.value());
 }
 
 void PreviewsPageLoadMetricsObserver::OnFirstContentfulPaint(
     const page_load_metrics::PageLoadTiming& timing,
     const page_load_metrics::PageLoadExtraInfo& info) {
-  if (!is_offline_preview_ ||
-      !WasStartedInForegroundOptionalEventInForeground(
+  if (!WasStartedInForegroundOptionalEventInForeground(
           timing.dom_content_loaded_event_start, info)) {
     return;
   }
   PAGE_LOAD_HISTOGRAM(internal::kHistogramOfflinePreviewsFirstContentfulPaint,
                       timing.first_contentful_paint.value());
 }
 
 void PreviewsPageLoadMetricsObserver::OnParseStart(
     const page_load_metrics::PageLoadTiming& timing,
     const page_load_metrics::PageLoadExtraInfo& info) {
-  if (!is_offline_preview_ ||
-      !WasStartedInForegroundOptionalEventInForeground(
+  if (!WasStartedInForegroundOptionalEventInForeground(
           timing.dom_content_loaded_event_start, info)) {
     return;
   }
   PAGE_LOAD_HISTOGRAM(internal::kHistogramOfflinePreviewsParseStart,
                       timing.parse_start.value());
 }
 
 bool PreviewsPageLoadMetricsObserver::IsOfflinePreview(
     content::WebContents* web_contents) const {
 #if BUILDFLAG(ANDROID_JAVA_UI)
   offline_pages::OfflinePageTabHelper* tab_helper =
       offline_pages::OfflinePageTabHelper::FromWebContents(web_contents);
   return tab_helper && tab_helper->is_offline_preview();
 #else
   return false;
 #endif  // BUILDFLAG(ANDROID_JAVA_UI)
 }
 
 }  // namespace previews