Optional <TimeDelta> since they may be non existent.

components/page_load_metrics/browser/page_load_metrics_observer.h

 // 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.
 
 #ifndef COMPONENTS_PAGE_LOAD_METRICS_BROWSER_PAGE_LOAD_METRICS_OBSERVER_H_
 #define COMPONENTS_PAGE_LOAD_METRICS_BROWSER_PAGE_LOAD_METRICS_OBSERVER_H_
 
 #include "base/macros.h"
+#include "base/optional.h"
 #include "components/page_load_metrics/common/page_load_timing.h"
 #include "content/public/browser/navigation_handle.h"
 #include "url/gurl.h"
 
 namespace page_load_metrics {
 
 // This enum represents how a page load ends. If the action occurs before the
 // page load finishes (or reaches some point like first paint), then we consider
 // the load to be aborted.
 enum UserAbortType {
@@ skipping 23 matching lines @@
 
   // The load aborted due to another navigation, but it isn't clear what type of
   // navigation it was.
   ABORT_UNKNOWN_NAVIGATION,
 
   // Add values before this final count.
   ABORT_LAST_ENTRY
 };
 
 struct PageLoadExtraInfo {
-  PageLoadExtraInfo(base::TimeDelta first_background_time,
-                    base::TimeDelta first_foreground_time,
-                    bool started_in_foreground,
-                    const GURL& committed_url,
-                    base::TimeDelta time_to_commit,
-                    UserAbortType abort_type,
-                    base::TimeDelta time_to_abort,
-                    const PageLoadMetadata& metadata);
+  PageLoadExtraInfo(
+      const base::Optional<base::TimeDelta>& first_background_time,
+      const base::Optional<base::TimeDelta>& first_foreground_time,
+      bool started_in_foreground,
+      const GURL& committed_url,
+      const base::Optional<base::TimeDelta>& time_to_commit,
+      UserAbortType abort_type,
+      const base::Optional<base::TimeDelta>& time_to_abort,
+      const PageLoadMetadata& metadata);
+
   PageLoadExtraInfo(const PageLoadExtraInfo& other);
 
+  ~PageLoadExtraInfo();
+
   // The first time that the page was backgrounded since the navigation started.
-  // If the page has not been backgrounded this will be base::TimeDelta().
-  const base::TimeDelta first_background_time;
+  const base::Optional<base::TimeDelta> first_background_time;
 
   // The first time that the page was foregrounded since the navigation started.
-  // If the page has not been foregrounded this will be base::TimeDelta().
-  const base::TimeDelta first_foreground_time;
+  const base::Optional<base::TimeDelta> first_foreground_time;
 
   // True if the page load started in the foreground.
   const bool started_in_foreground;
 
   // Committed URL. If the page load did not commit, |committed_url| will be
   // empty.
   const GURL committed_url;
 
-  // Time from navigation start until commit. If the page load did not commit,
-  // |time_to_commit| will be zero.
-  const base::TimeDelta time_to_commit;
+  // Time from navigation start until commit.
+  const base::Optional<base::TimeDelta> time_to_commit;
 
   // The abort time and time to abort for this page load. If the page was not
-  // aborted, |abort_type| will be |ABORT_NONE| and |time_to_abort| will be
-  // |base::TimeDelta()|.
+  // aborted, |abort_type| will be |ABORT_NONE|

[Charlie Harrison, 2016/05/19 18:20:49]

Add a period at the end of the sentence.

[shivanisha, 2016/05/23 15:06:44]

done

   const UserAbortType abort_type;
-  const base::TimeDelta time_to_abort;
+  const base::Optional<base::TimeDelta> time_to_abort;
 
   // Extra information supplied to the page load metrics system from the
   // renderer.
   const PageLoadMetadata metadata;
 };
 
 // Interface for PageLoadMetrics observers. All instances of this class are
 // owned by the PageLoadTracker tracking a page load. They will be deleted after
 // calling OnComplete.
 class PageLoadMetricsObserver {
@@ skipping 66 matching lines @@
                                       const PageLoadExtraInfo& extra_info) {}
   virtual void OnParseStart(const PageLoadTiming& timing,
                             const PageLoadExtraInfo& extra_info) {}
   virtual void OnParseStop(const PageLoadTiming& timing,
                            const PageLoadExtraInfo& extra_info) {}
 };
 
 }  // namespace page_load_metrics
 
 #endif  // COMPONENTS_PAGE_LOAD_METRICS_BROWSER_PAGE_LOAD_METRICS_OBSERVER_H_