Add time-to-first-contentful-paint to PageLoadMetrics

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 "base/location.h"
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
 #include "components/page_load_metrics/browser/page_load_metrics_macros.h"
@@ skipping 66 matching lines @@
 base::Time WallTimeFromTimeTicks(base::TimeTicks time) {
   return base::Time::FromDoubleT(
       (time - base::TimeTicks::UnixEpoch()).InSecondsF());
 }
 
 void RecordInternalError(InternalErrorLoadEvent event) {
   UMA_HISTOGRAM_ENUMERATION(
       "PageLoad.Events.InternalError", event, ERR_LAST_ENTRY);
 }
 
+base::TimeDelta FirstContentfulPaint(const PageLoadTiming& timing) {

[kinuko, 2015/10/29 07:14:04]

naming-nit: GetFirstContent... ?
 

[Kunihiko Sakamoto, 2015/10/29 08:00:09]

Done.

+  if (timing.first_text_paint.is_zero())
+    return timing.first_image_paint;
+  if (timing.first_image_paint.is_zero())
+    return timing.first_text_paint;
+  return std::min(timing.first_text_paint, timing.first_image_paint);
+}
+
 }  // namespace
 
 PageLoadTracker::PageLoadTracker(
     bool in_foreground,
     base::ObserverList<PageLoadMetricsObserver, true>* observers)
     : has_commit_(false),
       started_in_foreground_(in_foreground),
       observers_(observers) {}
 
 PageLoadTracker::~PageLoadTracker() {
@@ skipping 137 matching lines @@
   if (!timing_.first_image_paint.is_zero()) {
     if (timing_.first_image_paint < background_delta) {
       PAGE_LOAD_HISTOGRAM("PageLoad.Timing2.NavigationToFirstImagePaint",
                           timing_.first_image_paint);
     } else {
       PAGE_LOAD_HISTOGRAM(
           "PageLoad.Timing2.NavigationToFirstImagePaint.Background",
           timing_.first_image_paint);
     }
   }
+  base::TimeDelta first_contentful_paint = FirstContentfulPaint(timing_);
+  if (!first_contentful_paint.is_zero()) {
+    if (first_contentful_paint < background_delta) {
+      PAGE_LOAD_HISTOGRAM("PageLoad.Timing2.NavigationToFirstContentfulPaint",
+                          first_contentful_paint);
+    } else {
+      PAGE_LOAD_HISTOGRAM(
+          "PageLoad.Timing2.NavigationToFirstContentfulPaint.Background",
+          first_contentful_paint);
+    }
+  }
+
   // Log time to first foreground / time to first background. Log counts that we
   // started a relevant page load in the foreground / background.
   if (!background_time_.is_null()) {
     PAGE_LOAD_HISTOGRAM("PageLoad.Timing2.NavigationToFirstBackground",
                         background_delta);
   } else if (!foreground_time_.is_null()) {
     PAGE_LOAD_HISTOGRAM(
         "PageLoad.Timing2.NavigationToFirstForeground",
         WallTimeFromTimeTicks(foreground_time_) - timing_.navigation_start);
   }
@@ skipping 185 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