Use lossy prefs in the net predictor, and update them more frequently

chrome/browser/net/predictor.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.
 
 // A Predictor object is instantiated once in the browser process, and manages
 // both preresolution of hostnames, as well as TCP/IP preconnection to expected
 // subresources.
 // Most hostname lists are provided by the renderer processes, and include URLs
 // that *might* be used in the near future by the browsing user.  One goal of
 // this class is to cause the underlying DNS structure to lookup a hostname
@@ skipping 154 matching lines @@
   // Clears the preferences used by the predictor. Must be called on the UI
   // thread.
   void ClearPrefsOnUIThread();
 
   static void set_max_queueing_delay(int max_queueing_delay_ms);
 
   static void set_max_parallel_resolves(size_t max_parallel_resolves);
 
   virtual void ShutdownOnUIThread();
 
+  void UpdatePrefsOnUIThread(std::unique_ptr<base::ListValue> startup_list,
+                             std::unique_ptr<base::ListValue> referral_list);
+
   // ------------- End UI thread methods.
 
   // ------------- Start IO thread methods.
 
+  void WriteDnsPrefetchState(base::ListValue* startup_list,
+                             base::ListValue* referral_list);
+
   // Cancel pending requests and prevent new ones from being made.
   void Shutdown();
 
   // In some circumstances, for privacy reasons, all results should be
   // discarded.  This method gracefully handles that activity.
   // Destroy all our internal state, which shows what names we've looked up, and
   // how long each has taken, etc. etc.  We also destroy records of suggesses
   // (cache hits etc.).
   void DiscardAllResults();
 
@@ skipping 42 matching lines @@
 
   // Renderer bundles up list and sends to this browser API via IPC.
   // TODO(csharrison): Use a GURL vector instead to include port and scheme.
   void DnsPrefetchList(const std::vector<std::string>& hostnames);
 
   // May be called from either the IO or UI thread and will PostTask
   // to the IO thread if necessary.
   void DnsPrefetchMotivatedList(const std::vector<GURL>& urls,
                                 UrlInfo::ResolutionMotivation motivation);
 
-  // May be called from either the IO or UI thread and will PostTask
-  // to the IO thread if necessary.
+  // Called from the UI thread in response to the load event.
   void SaveStateForNextStartup();
 
-  void SaveDnsPrefetchStateForNextStartup(base::ListValue* startup_list,
-                                          base::ListValue* referral_list,
-                                          base::WaitableEvent* completion);
-
   // May be called from either the IO or UI thread and will PostTask
   // to the IO thread if necessary.
   void PreconnectUrl(const GURL& url,
                      const GURL& first_party_for_cookies,
                      UrlInfo::ResolutionMotivation motivation,
                      bool allow_credentials,
                      int count);
 
   void PreconnectUrlOnIOThread(const GURL& url,
                                const GURL& first_party_for_cookies,
@@ skipping 274 matching lines @@
   // we have a Referrer list. Each Referrer list has all hostnames we might
   // need to pre-resolve or pre-connect to when there is a navigation to the
   // orginial hostname.
   Referrers referrers_;
 
   // An observer for testing.
   PredictorObserver* observer_;
 
   std::unique_ptr<TimedCache> timed_cache_;
 
-  std::unique_ptr<base::WeakPtrFactory<Predictor>> weak_factory_;
+  // TODO(csharrison): It is not great that two weak pointer factories are
+  // needed in this class. Let's split it into two classes that live on each
+  // thread.
+  //
+  // Weak factory for weak pointers that should be dereferenced on the IO
+  // thread.
+  std::unique_ptr<base::WeakPtrFactory<Predictor>> io_weak_factory_;
+  // Weak factory for weak pointers that should be dereferenced on the UI

[Bernhard Bauer, 2016/08/01 09:06:24]

Nit: Empty line before the comment?

[Charlie Harrison, 2016/08/01 12:38:24]

Done.

+  // thread.
+  std::unique_ptr<base::WeakPtrFactory<Predictor>> ui_weak_factory_;
 
   // Protects |preconnect_enabled_|.
   mutable base::Lock preconnect_enabled_lock_;
 
   DISALLOW_COPY_AND_ASSIGN(Predictor);
 };
 
 // This version of the predictor is used for testing.
 class SimplePredictor : public Predictor {
  public:
   explicit SimplePredictor(bool preconnect_enabled, bool predictor_enabled)
       : Predictor(preconnect_enabled, predictor_enabled) {}
   ~SimplePredictor() override {}
   void InitNetworkPredictor(PrefService* user_prefs,
                             IOThread* io_thread,
                             net::URLRequestContextGetter* getter,
                             ProfileIOData* profile_io_data) override;
   void ShutdownOnUIThread() override;
 
  private:
   // These member functions return True for unittests.
   bool CanPrefetchAndPrerender() const override;
   bool CanPreresolveAndPreconnect() const override;
 };
 
 }  // namespace chrome_browser_net
 
 #endif  // CHROME_BROWSER_NET_PREDICTOR_H_