Convert first contentful paint logging to the new UKM client API

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 "chrome/browser/page_load_metrics/page_load_metrics_util.h"
 #include "components/ukm/ukm_service.h"
-#include "components/ukm/ukm_source.h"
+
+namespace internal {
+
+const char kUkmPageLoadEventName[] = "PageLoad";
+const char kUkmFirstContentfulPaintName[] =
+    "PaintTiming.NavigationToFirstContentfulPaint";
+
+}  // namespace internal
+
+namespace {
+
+// We need to provide a unique GlobalRequestID for each page load. Ideally, we'd
+// use the GlobalRequestID of the main resource request of the page load, but
+// the content API doesn't yet provide a convenient way to discover the
+// GlobalRequestID early in the navigation flow. Thus, until
+// https://docs.google.com/document/d/1FqxC_mgBEi5N1tVCxgj3M7P2yrRTOdxZdShzEpxdknM/edit
+// is addressed, we synthesize a fake GlobalRequestID for each new page load.
+content::GlobalRequestID NewGlobalRequestID() {
+  // We use int_max as our fake child_id value to minimize the chances of
+  // colliding with a real GlobalRequestID value from another UKM client.
+  static constexpr int kFakeChildId = std::numeric_limits<int>::max();
+
+  static int unique_identifier = 0;
+  return content::GlobalRequestID(kFakeChildId, unique_identifier++);
+}
+
+}  // namespace
 
 // 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::UkmPageLoadMetricsObserver()
+    : global_request_id_(NewGlobalRequestID()) {}
+
+UkmPageLoadMetricsObserver::~UkmPageLoadMetricsObserver() = default;
 
 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;
+  if (!started_in_foreground)
+    return STOP_OBSERVING;
+
+  ukm::UkmService* ukm_service = g_browser_process->ukm_service();
+  ukm_service->UpdateSourceURL(global_request_id_, navigation_handle->GetURL());
+  builder_ = ukm_service->GetEntryBuilder(global_request_id_,
+                                          internal::kUkmPageLoadEventName);
+  return CONTINUE_OBSERVING;
 }
 
 UkmPageLoadMetricsObserver::ObservePolicy
 UkmPageLoadMetricsObserver::FlushMetricsOnAppEnterBackground(
     const page_load_metrics::PageLoadTiming& timing,
     const page_load_metrics::PageLoadExtraInfo& info) {
-  SendMetricsToUkm(timing, info);
+  AddTimingMetrics(timing);
+  AddPageLoadExtraInfoMetrics(info, base::TimeTicks::Now());
   return STOP_OBSERVING;
 }
 
 UkmPageLoadMetricsObserver::ObservePolicy UkmPageLoadMetricsObserver::OnHidden(
     const page_load_metrics::PageLoadTiming& timing,
     const page_load_metrics::PageLoadExtraInfo& info) {
-  SendMetricsToUkm(timing, info);
+  AddTimingMetrics(timing);
+  AddPageLoadExtraInfoMetrics(info, base::TimeTicks());
   return STOP_OBSERVING;
 }
 
+void UkmPageLoadMetricsObserver::OnFailedProvisionalLoad(
+    const page_load_metrics::FailedProvisionalLoadInfo& failed_load_info,
+    const page_load_metrics::PageLoadExtraInfo& extra_info) {
+  AddPageLoadExtraInfoMetrics(extra_info, base::TimeTicks());
+}
+
 void UkmPageLoadMetricsObserver::OnComplete(
     const page_load_metrics::PageLoadTiming& timing,
     const page_load_metrics::PageLoadExtraInfo& info) {
-  SendMetricsToUkm(timing, info);
+  AddTimingMetrics(timing);
+  AddPageLoadExtraInfoMetrics(info, base::TimeTicks());
 }
 
-void UkmPageLoadMetricsObserver::SendMetricsToUkm(
-    const page_load_metrics::PageLoadTiming& timing,
-    const page_load_metrics::PageLoadExtraInfo& info) {
-  if (!info.did_commit || !timing.first_contentful_paint)
-    return;
+void UkmPageLoadMetricsObserver::AddTimingMetrics(
+    const page_load_metrics::PageLoadTiming& timing) {
+  if (timing.first_contentful_paint) {
+    builder_->AddMetric(internal::kUkmFirstContentfulPaintName,
+                        timing.first_contentful_paint.value().InMilliseconds());
+  }
+}
 
+void UkmPageLoadMetricsObserver::AddPageLoadExtraInfoMetrics(
+    const page_load_metrics::PageLoadExtraInfo& info,
+    base::TimeTicks app_background_time) {
   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.url);
-  source->set_first_contentful_paint(timing.first_contentful_paint.value());
-
-  ukm_service->RecordSource(std::move(source));
+  ukm_service->UpdateSourceURL(global_request_id_, info.url);
 }