prerender_manager.h revision 72a454cd3513ac24fbdd0e0cb9ad70b86a99b801 
1// Copyright (c) 2011 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef CHROME_BROWSER_PRERENDER_PRERENDER_MANAGER_H_
6#define CHROME_BROWSER_PRERENDER_PRERENDER_MANAGER_H_
7#pragma once
8
9#include <list>
10#include <vector>
11
12#include "base/ref_counted.h"
13#include "base/scoped_ptr.h"
14#include "base/time.h"
15#include "chrome/browser/prerender/prerender_contents.h"
16#include "googleurl/src/gurl.h"
17
18class Profile;
19class TabContents;
20
21// PrerenderManager is responsible for initiating and keeping prerendered
22// views of webpages.
23class PrerenderManager : public base::RefCounted<PrerenderManager> {
24 public:
25  // PrerenderManagerMode is used in a UMA_HISTOGRAM, so please do not
26  // add in the middle.
27  enum PrerenderManagerMode {
28    PRERENDER_MODE_DISABLED,
29    PRERENDER_MODE_ENABLED,
30    PRERENDER_MODE_EXPERIMENT_CONTROL_GROUP,
31    PRERENDER_MODE_EXPERIMENT_PRERENDER_GROUP,
32    PRERENDER_MODE_MAX
33  };
34
35  // Owned by a Profile object for the lifetime of the profile.
36  explicit PrerenderManager(Profile* profile);
37
38  // Preloads the URL supplied.  alias_urls indicates URLs that redirect
39  // to the same URL to be preloaded.
40  void AddPreload(const GURL& url, const std::vector<GURL>& alias_urls);
41
42  // For a given TabContents that wants to navigate to the URL supplied,
43  // determines whether a preloaded version of the URL can be used,
44  // and substitutes the prerendered RVH into the TabContents.  Returns
45  // whether or not a prerendered RVH could be used or not.
46  bool MaybeUsePreloadedPage(TabContents* tc, const GURL& url);
47
48  // Allows PrerenderContents to remove itself when prerendering should
49  // be cancelled.
50  void RemoveEntry(PrerenderContents* entry);
51
52  // Retrieves the PrerenderContents object for the specified URL, if it
53  // has been prerendered.  The caller will then have ownership of the
54  // PrerenderContents object and is responsible for freeing it.
55  // Returns NULL if the specified URL has not been prerendered.
56  PrerenderContents* GetEntry(const GURL& url);
57
58  // The following two methods should only be called from the UI thread.
59  void RecordPerceivedPageLoadTime(base::TimeDelta pplt);
60  void RecordTimeUntilUsed(base::TimeDelta time_until_used);
61
62  base::TimeDelta max_prerender_age() const { return max_prerender_age_; }
63  void set_max_prerender_age(base::TimeDelta td) { max_prerender_age_ = td; }
64  unsigned int max_elements() const { return max_elements_; }
65  void set_max_elements(unsigned int num) { max_elements_ = num; }
66
67  static PrerenderManagerMode GetMode();
68  static void SetMode(PrerenderManagerMode mode);
69  static bool IsPrerenderingEnabled();
70
71  // The following static method can be called from any thread, but will result
72  // in posting a task to the UI thread if we are not in the UI thread.
73  static void RecordPrefetchTagObserved();
74
75 protected:
76  virtual ~PrerenderManager();
77
78  void SetPrerenderContentsFactory(
79      PrerenderContents::Factory* prerender_contents_factory);
80
81 private:
82  // Test that needs needs access to internal functions.
83  friend class PrerenderBrowserTest;
84
85  friend class base::RefCounted<PrerenderManager>;
86  struct PrerenderContentsData;
87
88  bool IsPrerenderElementFresh(const base::Time start) const;
89  void DeleteOldEntries();
90  virtual base::Time GetCurrentTime() const;
91  virtual PrerenderContents* CreatePrerenderContents(
92      const GURL& url,
93      const std::vector<GURL>& alias_urls);
94
95  // Finds the specified PrerenderContents and returns it, if it exists.
96  // Returns NULL otherwise.  Unlike GetEntry, the PrerenderManager maintains
97  // ownership of the PrerenderContents.
98  PrerenderContents* FindEntry(const GURL& url);
99
100  bool ShouldRecordWindowedPPLT() const;
101
102  static void RecordPrefetchTagObservedOnUIThread();
103
104  Profile* profile_;
105
106  base::TimeDelta max_prerender_age_;
107  unsigned int max_elements_;
108
109  // List of prerendered elements.
110  std::list<PrerenderContentsData> prerender_list_;
111
112  // Default maximum permitted elements to prerender.
113  static const unsigned int kDefaultMaxPrerenderElements = 1;
114
115  // Default maximum age a prerendered element may have, in seconds.
116  static const int kDefaultMaxPrerenderAgeSeconds = 20;
117
118  // Time window for which we will record windowed PLT's from the last
119  // observed link rel=prefetch tag.
120  static const int kWindowedPPLTSeconds = 30;
121
122  scoped_ptr<PrerenderContents::Factory> prerender_contents_factory_;
123
124  static PrerenderManagerMode mode_;
125
126  // The time when we last saw a prefetch request coming from a renderer.
127  // This is used to record perceived PLT's for a certain amount of time
128  // from the point that we last saw a <link rel=prefetch> tag.
129  // This static variable should only be modified on the UI thread.
130  static base::TimeTicks last_prefetch_seen_time_;
131
132  DISALLOW_COPY_AND_ASSIGN(PrerenderManager);
133};
134
135#endif  // CHROME_BROWSER_PRERENDER_PRERENDER_MANAGER_H_
136