Optional <TimeDelta> since they may be non existent.

components/page_load_metrics/browser/metrics_web_contents_observer.h

Index: components/page_load_metrics/browser/metrics_web_contents_observer.h
diff --git a/components/page_load_metrics/browser/metrics_web_contents_observer.h b/components/page_load_metrics/browser/metrics_web_contents_observer.h
index d58cfb003b594b0b803b1b3b7fa8befb7d2354ab..37b760a5585773420fbd32bca1ddba5c1c38983b 100644
--- a/components/page_load_metrics/browser/metrics_web_contents_observer.h
+++ b/components/page_load_metrics/browser/metrics_web_contents_observer.h
@@ -143,8 +143,12 @@ class PageLoadTracker {
   // If the user performs some abort-like action while we are tracking this page
   // load, notify the tracker. Note that we may not classify this as an abort if
   // we've already performed a first paint.
-  void NotifyAbort(UserAbortType abort_type, base::TimeTicks timestamp);
-  void UpdateAbort(UserAbortType abort_type, base::TimeTicks timestamp);
+  void NotifyAbort(UserAbortType abort_type,
+                   base::TimeTicks timestamp,
+                   bool is_browser_timetick);
+  void UpdateAbort(UserAbortType abort_type,
+                   base::TimeTicks timestamp,
+                   bool is_browser_timetick);
 
   // This method returns true if this page load has been aborted with type of
   // ABORT_OTHER, and the |abort_cause_time| is within a sufficiently close
@@ -162,10 +166,21 @@ class PageLoadTracker {
   }
 
  private:
-  PageLoadExtraInfo GetPageLoadMetricsInfo();
+  PageLoadExtraInfo ComputePageLoadExtraInfo();
+
+#if defined(OS_WIN)
+  // This function converts a TimeTicks value taken in the browser process
+  // to navigation_start_ if:
+  // - base::TimeTicks is not comparable across processes because the clock
+  // is not system wide monotonic.
+  // - event_time < navigation_start_
+  void RebaseBrowserTimestampIfInterProcessTimeTickSkew(
+      base::TimeTicks& event_time);
+#endif
 
   void UpdateAbortInternal(UserAbortType abort_type,
-                           base::TimeTicks timestamp);
+                           base::TimeTicks timestamp,
+                           bool is_browser_timetick);
 
   // If |final_navigation| is null, then this is an "unparented" abort chain,
   // and represents a sequence of provisional aborts that never ends with a
@@ -258,7 +273,8 @@ class MetricsWebContentsObserver
   // that might abort them.
   void NotifyAbortAllLoads(UserAbortType abort_type);
   void NotifyAbortAllLoadsWithTimestamp(UserAbortType abort_type,
-                                        base::TimeTicks timestamp);
+                                        base::TimeTicks timestamp,
+                                        bool is_browser_timestamp);
   // Notify aborted provisional loads that a new navigation occurred. This is
   // used for more consistent attribution tracking for aborted provisional
   // loads. This method returns the provisional load that was likely aborted by