[Prerender] first contentful paint histograms.

chrome/browser/page_load_metrics/observers/prerender_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/prerender_page_load_metrics_observer.h"
+
+#include "base/logging.h"
+#include "base/memory/ptr_util.h"
+#include "chrome/browser/prerender/prerender_manager.h"
+#include "chrome/browser/prerender/prerender_manager_factory.h"
+#include "content/public/browser/web_contents.h"
+#include "net/http/http_response_headers.h"
+
+// static
+std::unique_ptr<page_load_metrics::PageLoadMetricsObserver>
+PrerenderPageLoadMetricsObserver::CreateIfNeeded(
+    content::WebContents* web_contents) {
+  prerender::PrerenderManager* manager =
+      prerender::PrerenderManagerFactory::GetForBrowserContext(
+          web_contents->GetBrowserContext());
+  if (!manager)
+    return nullptr;
+
+  if (manager->PageLoadMetricsObserverDisabledForTesting())
+    return nullptr;
+
+  return base::MakeUnique<PrerenderPageLoadMetricsObserver>(manager,
+                                                            web_contents);
+}
+
+PrerenderPageLoadMetricsObserver::PrerenderPageLoadMetricsObserver(
+    prerender::PrerenderManager* manager,
+    content::WebContents* web_contents)
+    : prerender_manager_(manager),
+      web_contents_(web_contents),
+      is_no_store_(false),
+      was_hidden_(false) {
+  DCHECK(prerender_manager_);
+  DCHECK(web_contents_);
+}
+
+page_load_metrics::PageLoadMetricsObserver::ObservePolicy
+PrerenderPageLoadMetricsObserver::OnStart(
+    content::NavigationHandle* navigation_handle,
+    const GURL& currently_committed_url,
+    bool started_in_foreground) {
+  DCHECK(!started_in_foreground);
+
+  start_ticks_ = navigation_handle->NavigationStart();
+  return CONTINUE_OBSERVING;
+}
+
+page_load_metrics::PageLoadMetricsObserver::ObservePolicy
+PrerenderPageLoadMetricsObserver::OnCommit(
+    content::NavigationHandle* navigation_handle) {
+  const net::HttpResponseHeaders* response_headers =
+      navigation_handle->GetResponseHeaders();
+
+  is_no_store_ = response_headers &&
+                 response_headers->HasHeaderValue("cache-control", "no-store");
+  return CONTINUE_OBSERVING;
+}
+
+void PrerenderPageLoadMetricsObserver::OnFirstContentfulPaint(
+    const page_load_metrics::PageLoadTiming& timing,
+    const page_load_metrics::PageLoadExtraInfo& extra_info) {
+  DCHECK(!start_ticks_.is_null());
+  prerender_manager_->RecordPrerenderFirstContentfulPaint(
+      extra_info.start_url, web_contents_, is_no_store_, was_hidden_,
+      start_ticks_ + *timing.first_contentful_paint);
+}
+
+page_load_metrics::PageLoadMetricsObserver::ObservePolicy
+PrerenderPageLoadMetricsObserver::OnHidden(
+    const page_load_metrics::PageLoadTiming& timing,
+    const page_load_metrics::PageLoadExtraInfo& extra_info) {
+  was_hidden_ = true;
+  return CONTINUE_OBSERVING;
+}
+
+void PrerenderPageLoadMetricsObserver::SetNavigationStartTicksForTesting(
+    base::TimeTicks ticks) {
+  start_ticks_ = ticks;
+}