[NoStatePrefetch] Add performance histograms.

chrome/browser/page_load_metrics/observers/no_state_prefetch_page_load_metrics_observer.cc

Index: chrome/browser/page_load_metrics/observers/no_state_prefetch_page_load_metrics_observer.cc
diff --git a/chrome/browser/page_load_metrics/observers/no_state_prefetch_page_load_metrics_observer.cc b/chrome/browser/page_load_metrics/observers/no_state_prefetch_page_load_metrics_observer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..d3d2575e66d5800236ad2f311ac705805ffe185c
--- /dev/null
+++ b/chrome/browser/page_load_metrics/observers/no_state_prefetch_page_load_metrics_observer.cc
@@ -0,0 +1,53 @@
+// 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/no_state_prefetch_page_load_metrics_observer.h"
+
+#include "chrome/browser/prerender/prerender_manager.h"
+#include "chrome/browser/prerender/prerender_manager_factory.h"
+#include "content/public/browser/navigation_handle.h"
+#include "content/public/browser/web_contents.h"
+#include "net/http/http_response_headers.h"
+
+NoStatePrefetchPageLoadMetricsObserver::NoStatePrefetchPageLoadMetricsObserver()
+    : is_no_store_(false), navigation_committed_(false) {}
+
+NoStatePrefetchPageLoadMetricsObserver::
+    ~NoStatePrefetchPageLoadMetricsObserver() {}
+
+void NoStatePrefetchPageLoadMetricsObserver::OnStart(
+    content::NavigationHandle* navigation_handle,
+    const GURL& currently_committed_url,
+    bool started_in_foreground) {
+  url_ = navigation_handle->GetURL();
+  prerender::PrerenderManager* manager =
+      prerender::PrerenderManagerFactory::GetForBrowserContext(
+          navigation_handle->GetWebContents()->GetBrowserContext());
+  if (manager)
+    prerender_manager_ = manager->AsWeakPtr();

[Charlie Harrison, 2016/09/15 13:41:33]

I wonder if we can avoid setting this observer if there is no manager in a
create() static method or something? This would avoid allocation for non
prerenderer pages (or pages without a a prerender_manager).

[Charlie Harrison, 2016/09/15 13:41:33]

Be mindful that we turn off page load metrics for prerenderer pages (see
PageLoadMetricsEmbedder::IsPrerendering and uses). Make sure that that won't
interfere with any logging that you want to do.

[droger, 2016/09/15 15:06:33]

As far as I know, this is only happening in unit tests. I see no harm in doing
it though.
Done.

[droger, 2016/09/15 15:06:33]

I know, and I actually don't want the metrics for the prerendered pages.

+}
+
+void NoStatePrefetchPageLoadMetricsObserver::OnCommit(
+    content::NavigationHandle* navigation_handle) {
+  navigation_committed_ = true;
+
+  const net::HttpResponseHeaders* response_headers =
+      navigation_handle->GetResponseHeaders();
+
+  is_no_store_ = response_headers &&
+                 response_headers->HasHeaderValue("cache-control", "no-store");
+}
+
+void NoStatePrefetchPageLoadMetricsObserver::OnFirstContentfulPaint(
+    const page_load_metrics::PageLoadTiming& timing,
+    const page_load_metrics::PageLoadExtraInfo& extra_info) {
+  DCHECK(navigation_committed_);
+
+  if (!prerender_manager_)
+    return;
+
+  DCHECK(timing.first_contentful_paint.has_value());
+  prerender_manager_->RecordFirstContentfulPaint(
+      url_, is_no_store_, *timing.first_contentful_paint);
+}