prerender_helper.h revision 5821806d5e7f356e8fa4b058a389a808ea183019 
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_RENDERER_PRERENDER_PRERENDER_HELPER_H_
6#define CHROME_RENDERER_PRERENDER_PRERENDER_HELPER_H_
7
8#include "base/compiler_specific.h"
9#include "base/time.h"
10#include "content/public/renderer/render_view_observer.h"
11#include "content/public/renderer/render_view_observer_tracker.h"
12
13namespace prerender {
14
15// Helper class to track whether its RenderView is currently being prerendered.
16// Also records prerendering-related histograms information and cancels
17// prerendering when necessary, based on observed events.  Created when
18// prerendering starts and deleted as soon as just after the prerendering
19// histograms have been recorded for a displayed prerendered page.  For
20// non-displayed pages, deleted on destruction of the RenderView.
21class PrerenderHelper
22    : public content::RenderViewObserver,
23      public content::RenderViewObserverTracker<PrerenderHelper> {
24 public:
25  explicit PrerenderHelper(content::RenderView* render_view);
26  virtual ~PrerenderHelper();
27
28  // Returns true if |render_view| is currently prerendering.
29  static bool IsPrerendering(const content::RenderView* render_view);
30
31  // Records prerender histograms.  These are recorded even for pages that are
32  // not prerendered, for comparison to pages that are.
33  static void RecordHistograms(
34      content::RenderView* render_view,
35      const base::Time& finish_all_loads,
36      const base::TimeDelta& begin_to_finish_all_loads);
37
38 private:
39  // RenderViewObserver implementation
40  virtual void DidStartProvisionalLoad(WebKit::WebFrame* frame) OVERRIDE;
41  virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE;
42
43  void OnSetIsPrerendering(bool is_prerendering);
44
45  // Returns true if the page is no longer being prerendered, but no histograms
46  // for the prerender have been recorded.
47  bool HasUnrecordedData() const;
48
49  // Updates the visibility state of the RenderView.  Must be called whenever
50  // prerendering starts or finishes.
51  void UpdateVisibilityState();
52
53  // Tracks whether or not observed RenderView is currently prerendering.
54  bool is_prerendering_;
55
56  // Time when the prerender started.
57  base::Time prerender_start_time_;
58  // Time when the prerendered page was displayed.
59  base::Time prerender_display_time_;
60
61  // Set to true when a prerendered page is displayed to prevent deletion from
62  // when a prerendered page is displayed until after the histograms for the
63  // page load have been recorded.
64  bool has_unrecorded_data_;
65
66  DISALLOW_COPY_AND_ASSIGN(PrerenderHelper);
67};
68
69}  // namespace prerender
70
71#endif  // CHROME_RENDERER_PRERENDER_PRERENDER_HELPER_H_
72