Add ReloadPageLoadMetricsObserver to have a metrics variant for reloads

chrome/browser/page_load_metrics/observers/reload_page_load_metrics_observer.cc

+// 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.
+
+#include "chrome/browser/page_load_metrics/observers/reload_page_load_metrics_observer.h"
+
+#include "chrome/browser/page_load_metrics/observers/core_page_load_metrics_observer.h"
+#include "components/page_load_metrics/browser/page_load_metrics_util.h"
+#include "ui/base/page_transition_types.h"
+
+namespace chrome {
+
+namespace {
+
+const char kHistogramFirstContentfulPaintReload[] =
+  "PageLoad.Reload.NavigationToFirstContentfulPaint";

[Bryan McQuade, 2016/05/25 22:53:29]

maybe PageLoad.PaintTiming.NavigationToFirstContentfulPaint.Reload?

should we use 'PageLoad.Clients' here? it's long, but it's consistent.

csharrison, wdyt?

[Takashi Toyoshima, 2016/05/26 06:06:50]

OK, I'll update my CL to use following names tentatively.
 -PageLoad.Clients.Reload.PaintTiming.NavigationToFirstContentfulPaint
 -PageLoad.Clients.Reload.PaintTiming.NavigationToFirstContentfulPaint.ByGesture

csharrison, please let me know if you have any idea.

+
+}  // namespace
+
+ReloadPageLoadMetricsObserver::ReloadPageLoadMetricsObserver()
+    : page_transition_was_reload_(false) {}
+
+void ReloadPageLoadMetricsObserver::OnCommit(
+    content::NavigationHandle* navigation_handle) {
+  page_transition_was_reload_ = ui::PageTransitionCoreTypeIs(

[Bryan McQuade, 2016/05/25 22:53:29]

if it's accurate, it'd be useful to store a variant of this metric for user
gesture reloads by storing the value of navigation_handle->HasUserGesture. That
way we avoid including automatic reloads for pages that reload in a tight loop.

[Takashi Toyoshima, 2016/05/26 06:06:50]

Done.

+      navigation_handle->GetPageTransition(), ui::PAGE_TRANSITION_RELOAD);
+}
+
+void ReloadPageLoadMetricsObserver::OnFirstContentfulPaint(
+    const page_load_metrics::PageLoadTiming& timing,
+    const page_load_metrics::PageLoadExtraInfo& extra_info) {
+  if (!page_transition_was_reload_ ||
+      !WasStartedInForegroundEventInForeground(timing.first_contentful_paint,
+                                               extra_info)) {
+    return;
+  }
+
+  PAGE_LOAD_HISTOGRAM(kHistogramFirstContentfulPaintReload,
+                      timing.first_contentful_paint);
+}
+
+}  // namespace chrome