Add NavigationToFirstContentfulPaint UMA for ServiceWorker controlled pages.

chrome/browser/page_load_metrics/observers/service_worker_page_load_metrics_observer.cc

Index: chrome/browser/page_load_metrics/observers/service_worker_page_load_metrics_observer.cc
diff --git a/chrome/browser/page_load_metrics/observers/service_worker_page_load_metrics_observer.cc b/chrome/browser/page_load_metrics/observers/service_worker_page_load_metrics_observer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..97bc2d210ad948ac3b5b6c792947c206485879c2
--- /dev/null
+++ b/chrome/browser/page_load_metrics/observers/service_worker_page_load_metrics_observer.cc
@@ -0,0 +1,47 @@
+// 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/service_worker_page_load_metrics_observer.h"
+
+#include "components/page_load_metrics/browser/page_load_metrics_util.h"
+#include "third_party/WebKit/public/platform/WebLoadingBehaviorFlag.h"
+
+namespace internal {
+
+const char kHistogramServiceWorkerFirstContentfulPaint[] =
+    "PageLoad.Clients.ServiceWorker.Timing2.NavigationToFirstContentfulPaint";
+const char kBackgroundHistogramServiceWorkerFirstContentfulPaint[] =
+    "PageLoad.Clients.ServiceWorker.Timing2.NavigationToFirstContentfulPaint."
+    "Background";
+
+}  // namespace internal
+
+ServiceWorkerPageLoadMetricsObserver::ServiceWorkerPageLoadMetricsObserver() {}
+
+void ServiceWorkerPageLoadMetricsObserver::OnComplete(
+    const page_load_metrics::PageLoadTiming& timing,
+    const page_load_metrics::PageLoadExtraInfo& info) {
+  if (timing.first_contentful_paint.is_zero())
+    return;
+  if (info.metadata.behavior_flags &
+      blink::WebLoadingBehaviorFlag::
+          WebLoadingBehaviorServiceWorkerControlled) {
+    LogServiceWorkerHistograms(timing, info);
+  }
+}
+
+void ServiceWorkerPageLoadMetricsObserver::LogServiceWorkerHistograms(
+    const page_load_metrics::PageLoadTiming& timing,
+    const page_load_metrics::PageLoadExtraInfo& info) {
+  bool foreground_paint = WasStartedInForegroundEventInForeground(
+      timing.first_contentful_paint, info);
+  if (foreground_paint) {
+    PAGE_LOAD_HISTOGRAM(internal::kHistogramServiceWorkerFirstContentfulPaint,
+                        timing.first_contentful_paint);
+  } else {
+    PAGE_LOAD_HISTOGRAM(
+        internal::kBackgroundHistogramServiceWorkerFirstContentfulPaint,
+        timing.first_contentful_paint);
+  }
+}