Histogram the amount of time spent on HTTP(S) page loads

chrome/browser/page_load_metrics/observers/https_page_load_metrics_observer.h

+// 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.
+
+#ifndef CHROME_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_HTTPS_PAGE_LOAD_METRICS_OBSERVER_H_
+#define CHROME_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_HTTPS_PAGE_LOAD_METRICS_OBSERVER_H_
+
+#include "base/macros.h"
+#include "base/time/time.h"
+#include "components/page_load_metrics/browser/page_load_metrics_observer.h"
+#include "url/gurl.h"
+
+class HttpsPageLoadMetricsObserver

[Charlie Harrison, 2016/04/25 13:20:08]

Can the class/file name be a bit more descriptive? Maybe
"HttpsEngagementPageLoadMetricsObserver"?

[felt, 2016/04/25 21:30:04]

Done.

+    : public page_load_metrics::PageLoadMetricsObserver {
+ public:
+  HttpsPageLoadMetricsObserver();
+
+  // page_load_metrics::PageLoadMetricsObserver implementation:

[Charlie Harrison, 2016/04/25 13:20:08]

page_load_metrics::PageLoadMetricsObserver:

[felt, 2016/04/25 21:30:04]

Done.

+  void OnCommit(content::NavigationHandle* navigation_handle,
+                bool started_in_foreground) override;
+  void OnHidden() override;
+  void OnShown() override;
+  void OnComplete(
+      const page_load_metrics::PageLoadTiming& timing,
+      const page_load_metrics::PageLoadExtraInfo& extra_info) override;
+
+ private:
+  GURL url_;

[Charlie Harrison, 2016/04/25 13:20:08]

PageLoadExtraInfo has the committed_url in OnComplete, which should be enough
for you. If you only filter by committed loads you can use that and avoid this
copy.

[felt, 2016/04/25 21:30:04]

Done.

+  bool currently_in_foreground_;
+  base::TimeDelta foreground_time_;
+  base::Time last_time_shown_;

[Charlie Harrison, 2016/04/25 13:20:08]

Why not use a TimeTicks here? Do you need to correlate with a date?

[felt, 2016/04/25 21:30:04]

Done.

+  bool time_travelled_backwards_;
+
+  DISALLOW_COPY_AND_ASSIGN(HttpsPageLoadMetricsObserver);
+};
+
+#endif  // CHROME_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_HTTPS_PAGE_LOAD_METRICS_OBSERVER_H_