Optional <TimeDelta> since they may be non existent.

components/page_load_metrics/browser/metrics_web_contents_observer.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/metrics_web_contents_observer.h"
 
 #include <algorithm>
 #include <string>
 #include <utility>
 
@@ skipping 173 matching lines @@
       aborted_chain_size_same_url_(aborted_chain_size_same_url),
       embedder_interface_(embedder_interface) {
   DCHECK(!navigation_handle->HasCommitted());
   embedder_interface_->RegisterObservers(this);
   for (const auto& observer : observers_) {
     observer->OnStart(navigation_handle);
   }
 }
 
 PageLoadTracker::~PageLoadTracker() {
-  const PageLoadExtraInfo info = GetPageLoadMetricsInfo();
-  if (!info.time_to_commit.is_zero() && renderer_tracked() &&
-      timing_.IsEmpty()) {
+  const PageLoadExtraInfo info = ComputePageLoadExtraInfo();
+
+  if (!info.time_to_commit && renderer_tracked() && timing_.IsEmpty()) {
     RecordInternalError(ERR_NO_IPCS_RECEIVED);
   }
   // Recall that trackers that are given ABORT_UNKNOWN_NAVIGATION have their
   // chain length added to the next navigation. Take care not to double count
   // them. Also do not double count committed loads, which call this already.
   if (commit_time_.is_null() && abort_type_ != ABORT_UNKNOWN_NAVIGATION)
     LogAbortChainHistograms(nullptr);
 
   for (const auto& observer : observers_) {
     observer->OnComplete(timing_, info);
@@ skipping 112 matching lines @@
 
 void PageLoadTracker::set_renderer_tracked(bool renderer_tracked) {
   renderer_tracked_ = renderer_tracked;
 }
 
 void PageLoadTracker::AddObserver(
     scoped_ptr<PageLoadMetricsObserver> observer) {
   observers_.push_back(std::move(observer));
 }
 
-PageLoadExtraInfo PageLoadTracker::GetPageLoadMetricsInfo() {
-  base::TimeDelta first_background_time;
-  base::TimeDelta first_foreground_time;
-  base::TimeDelta time_to_abort;
-  base::TimeDelta time_to_commit;
+PageLoadExtraInfo PageLoadTracker::ComputePageLoadExtraInfo() {
+  base::Optional<base::TimeDelta> first_background_time;
+  base::Optional<base::TimeDelta> first_foreground_time;
+  base::Optional<base::TimeDelta> time_to_abort;
+  base::Optional<base::TimeDelta> time_to_commit;
   if (!background_time_.is_null())
     first_background_time = background_time_ - navigation_start_;
   if (!foreground_time_.is_null())
     first_foreground_time = foreground_time_ - navigation_start_;
   if (abort_type_ != ABORT_NONE) {
-    DCHECK_GT(abort_time_, navigation_start_);
+    DCHECK_GE(abort_time_, navigation_start_);
     time_to_abort = abort_time_ - navigation_start_;
   } else {
     DCHECK(abort_time_.is_null());
   }
 
   if (!commit_time_.is_null()) {
-    DCHECK_GT(commit_time_, navigation_start_);
+    DCHECK_GE(commit_time_, navigation_start_);
     time_to_commit = commit_time_ - navigation_start_;
-  } else {
-    DCHECK(commit_time_.is_null());
   }
   return PageLoadExtraInfo(first_background_time, first_foreground_time,
                            started_in_foreground_,
                            commit_time_.is_null() ? GURL() : url_,
                            time_to_commit, abort_type_, time_to_abort);
 }
 
 void PageLoadTracker::NotifyAbort(UserAbortType abort_type,
                                   base::TimeTicks timestamp) {
   DCHECK_NE(abort_type, ABORT_NONE);
@@ skipping 35 matching lines @@
                                           base::TimeTicks timestamp) {
   // When a provisional navigation commits, that navigation's start time is
   // interpreted as the abort time for other provisional loads in the tab.
   // However, this only makes sense if the committed load started after the
   // aborted provisional loads started. Thus we ignore cases where the committed
   // load started before the aborted provisional load, as this would result in
   // recording a negative time-to-abort. The real issue here is that we have to
   // infer the cause of aborts. It would be better if the navigation code could
   // instead report the actual cause of an aborted navigation. See crbug/571647
   // for details.
-  if (timestamp <= navigation_start_) {
+  if (timestamp < navigation_start_) {
     RecordInternalError(ERR_ABORT_BEFORE_NAVIGATION_START);
     abort_type_ = ABORT_NONE;
     abort_time_ = base::TimeTicks();
     return;
   }
   abort_type_ = abort_type;
   abort_time_ = timestamp;
 }
 
 // static
@@ skipping 264 matching lines @@
 
   if (!committed_load_->UpdateTiming(timing)) {
     // If the page load tracker cannot update its timing, something is wrong
     // with the IPC (it's from another load, or it's invalid in some other way).
     // We expect this to be a rare occurrence.
     RecordInternalError(ERR_BAD_TIMING_IPC);
   }
 }
 
 }  // namespace page_load_metrics