PageLoadMetrics renderer and browser implementation (deprecated)

components/page_load_metrics/common/page_load_timing.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_COMMON_PAGE_LOAD_TIMING_H_
+#define COMPONENTS_PAGE_LOAD_METRICS_COMMON_PAGE_LOAD_TIMING_H_
+
+#include "base/time/time.h"
+
+namespace page_load_metrics {
+
+// PageLoadTiming contains timing metrics associated with a page load. Many of
+// the metrics here are based on the Navigation Timing spec:
+// http://www.w3.org/TR/navigation-timing/.
+struct PageLoadTiming {
+ public:
+  PageLoadTiming();
+  ~PageLoadTiming();
+
+  bool operator==(const PageLoadTiming& other) const;

[Randy Smith (Not in Mondays), 2015/08/26 19:11:48]

I have no objection, but document why this is needed and what semantics it
exports?  If it's all member equals, maybe = default
(http://chromium-cpp.appspot.com/ -> "Default Function Creation") would be
appropriate?

+
+  // Time that the navigation for the associated page was initiated.
+  base::Time navigation_start;
+
+  // Time that the first byte of the response is received.
+  base::Time response_start;
+
+  // Time immediately before the DOMContentLoaded event is fired.
+  base::Time dom_content_loaded_event_start;
+
+  // Time immediately before the load event is fired.
+  base::Time load_event_start;
+
+  // Time when the first layout is completed.
+  base::Time first_layout;

[Randy Smith (Not in Mondays), 2015/08/26 19:11:48]

As I understand it (please correct me if I'm wrong) on any particular message
any of these may not have been set.  How is that signaled?  Null Time()? 
However it's signaled, I think that it should be documented, both that they can
be null and what they are if they're null.

+
+  // If you add additional members, also be sure to update operator== and
+  // page_load_metrics_messages.h
+};
+
+}  // namespace page_load_metrics
+
+#endif  // COMPONENTS_PAGE_LOAD_METRICS_COMMON_PAGE_LOAD_TIMING_H_