Added UkmPageLoadMetricsObserver which sends top-level metrics to UKM

chrome/browser/page_load_metrics/observers/ukm_page_load_metrics_observer.cc

+// Copyright 2017 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/ukm_page_load_metrics_observer.h"
+#include "chrome/browser/browser_process.h"
+#include "components/ukm/ukm_service.h"
+#include "components/ukm/ukm_source.h"
+
+// static
+std::unique_ptr<page_load_metrics::PageLoadMetricsObserver>
+UkmPageLoadMetricsObserver::CreateIfNeeded() {
+  if (!g_browser_process->ukm_service()) {
+    return nullptr;
+  }
+
+  return base::MakeUnique<UkmPageLoadMetricsObserver>();
+}
+
+UkmPageLoadMetricsObserver::UkmPageLoadMetricsObserver() {}
+
+UkmPageLoadMetricsObserver::ObservePolicy UkmPageLoadMetricsObserver::OnStart(
+    content::NavigationHandle* navigation_handle,
+    const GURL& currently_committed_url,
+    bool started_in_foreground) {
+  return started_in_foreground ? CONTINUE_OBSERVING : STOP_OBSERVING;
+}
+
+UkmPageLoadMetricsObserver::ObservePolicy
+UkmPageLoadMetricsObserver::FlushMetricsOnAppEnterBackground(
+    const page_load_metrics::PageLoadTiming& timing,
+    const page_load_metrics::PageLoadExtraInfo& info) {
+  SendMetricsToUkm(timing, info);
+  return STOP_OBSERVING;
+}
+
+UkmPageLoadMetricsObserver::ObservePolicy UkmPageLoadMetricsObserver::OnHidden(
+    const page_load_metrics::PageLoadTiming& timing,
+    const page_load_metrics::PageLoadExtraInfo& info) {
+  SendMetricsToUkm(timing, info);
+  return STOP_OBSERVING;
+}
+
+void UkmPageLoadMetricsObserver::OnComplete(
+    const page_load_metrics::PageLoadTiming& timing,
+    const page_load_metrics::PageLoadExtraInfo& info) {
+  SendMetricsToUkm(timing, info);
+}
+
+void UkmPageLoadMetricsObserver::SendMetricsToUkm(
+    const page_load_metrics::PageLoadTiming& timing,
+    const page_load_metrics::PageLoadExtraInfo& info) {
+  if (info.committed_url.is_empty() || !timing.first_contentful_paint)
+    return;
+
+  ukm::UkmService* ukm_service = g_browser_process->ukm_service();
+  DCHECK(ukm_service);
+
+  std::unique_ptr<ukm::UkmSource> source = base::MakeUnique<ukm::UkmSource>();
+  source->set_committed_url(info.committed_url);
+  source->set_first_contentful_paint(timing.first_contentful_paint.value());

[Bryan McQuade, 2017/01/31 22:31:54]

just realized that timing.first_contentful_paint may not always be set when this
is called, and thus timing.first_contentful_paint.value() will assert. I'll send
a patch to address this shortly.

+
+  ukm_service->RecordSource(std::move(source));
+}