Don't log background navigations in StaleWhileRevalidateExperiment histograms

components/page_load_metrics/browser/page_load_metrics_util.cc

 // Copyright 2015 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 "components/page_load_metrics/browser/page_load_metrics_util.h"
 
 #include <algorithm>
 
 #include "components/page_load_metrics/common/page_load_timing.h"
 
 namespace page_load_metrics {
 
 base::TimeDelta GetFirstContentfulPaint(const PageLoadTiming& timing) {
   if (timing.first_text_paint.is_zero())
     return timing.first_image_paint;
   if (timing.first_image_paint.is_zero())
     return timing.first_text_paint;
   return std::min(timing.first_text_paint, timing.first_image_paint);
 }
 
+bool EventOccurredInForeground(const base::TimeDelta& event,
+                               const base::TimeDelta& first_background) {
+  return !event.is_zero() &&
+         (first_background.is_zero() || event < first_background);
+}
+
 }  // namespace page_load_metrics
-