[NoStatePrefetch] Add performance histograms.

chrome/browser/prerender/prerender_manager.h

 // Copyright (c) 2012 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.
 
 #ifndef CHROME_BROWSER_PRERENDER_PRERENDER_MANAGER_H_
 #define CHROME_BROWSER_PRERENDER_PRERENDER_MANAGER_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 198 matching lines @@
                                       bool is_main_resource,
                                       bool is_redirect,
                                       bool is_no_store);
 
   // Called when a NoStatePrefetch resource has been loaded. This is called only
   // once per resource, when all redirects have been resolved.
   void RecordPrefetchRedirectCount(Origin origin,
                                    bool is_main_resource,
                                    int redirect_count);
 
+  // Records the time to first contentful paint.
+  // |is_no_store| must be true if the main resource has a "no-store" cache
+  // control HTTP header.
+  void RecordFirstContentfulPaint(const GURL& url,
+                                  bool is_no_store,
+                                  base::TimeDelta time);

[mmenke, 2016/09/16 16:53:48]

Oh, this does something completely different from what I assumed it did.  Could
we make it clearer that this is for recording the time of a non-prefetched page,
after it was previously prefetched, and rename the method as well to make that
clearer?

[droger, 2016/09/19 09:55:23]

Note that prefetched pages are not rendered at all, so the "first contentful
paint" does not mean anything for them.

Added a comment.

+
   static PrerenderManagerMode GetMode();
   static void SetMode(PrerenderManagerMode mode);
   static bool IsPrerenderingPossible();
   static bool ActuallyPrerendering();
   static bool IsControlGroup();
   static bool IsNoUseGroup();
   static bool IsNoStatePrefetch();
 
   // Query the list of current prerender pages to see if the given web contents
   // is prerendering a page. The optional parameter |origin| is an output
@@ skipping 265 matching lines @@
       PrerenderContents* prerender_contents);
 
   bool DoesRateLimitAllowPrerender(Origin origin) const;
 
   // Deletes old WebContents that have been replaced by prerendered ones.  This
   // is needed because they're replaced in a callback from the old WebContents,
   // so cannot immediately be deleted.
   void DeleteOldWebContents();
 
   // Cleans up old NavigationRecord's.
-  void CleanUpOldNavigations();
+  void CleanUpOldNavigations(std::vector<NavigationRecord>* navigations,
+                             base::TimeDelta max_age);
 
   // Arrange for the given WebContents to be deleted asap. Delete |deleter| as
   // well.
   void ScheduleDeleteOldWebContents(std::unique_ptr<content::WebContents> tab,
                                     OnCloseWebContentsDeleter* deleter);
 
   // Adds to the history list.
   void AddToHistory(PrerenderContents* contents);
 
   // Returns a new Value representing the pages currently being prerendered.
@@ skipping 29 matching lines @@
   // All running prerenders. Sorted by expiry time, in ascending order.
   PrerenderDataVector active_prerenders_;
 
   // Prerenders awaiting deletion.
   PrerenderDataVector to_delete_prerenders_;
 
   // List of recent navigations in this profile, sorted by ascending
   // |navigate_time_|.
   std::vector<NavigationRecord> navigations_;
 
+  // List of recent prefetches, sorted by ascending navigate time.
+  std::vector<NavigationRecord> prefetches_;
+
   std::unique_ptr<PrerenderContents::Factory> prerender_contents_factory_;
 
   static PrerenderManagerMode mode_;
 
   // A count of how many prerenders we do per session. Initialized to 0 then
   // incremented and emitted to a histogram on each successful prerender.
   static int prerenders_per_session_count_;
 
   // RepeatingTimer to perform periodic cleanups of pending prerendered
   // pages.
@@ skipping 23 matching lines @@
   // Set of process hosts being prerendered.
   using PrerenderProcessSet = std::set<content::RenderProcessHost*>;
   PrerenderProcessSet prerender_process_hosts_;
 
   DISALLOW_COPY_AND_ASSIGN(PrerenderManager);
 };
 
 }  // namespace prerender
 
 #endif  // CHROME_BROWSER_PRERENDER_PRERENDER_MANAGER_H_