Move prerender histograms out of prerender manager.

chrome/browser/prerender/prerender_histograms.h

Index: chrome/browser/prerender/prerender_histograms.h
===================================================================
--- chrome/browser/prerender/prerender_histograms.h	(revision 0)
+++ chrome/browser/prerender/prerender_histograms.h	(revision 0)
@@ -0,0 +1,95 @@
+// Copyright (c) 2011 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_HISTOGRAMS_H_
+#define CHROME_BROWSER_PRERENDER_PRERENDER_HISTOGRAMS_H_
+#pragma once
+
+#include <string>
+
+#include "base/time.h"
+#include "chrome/browser/prerender/prerender_final_status.h"
+#include "chrome/browser/prerender/prerender_origin.h"
+#include "googleurl/src/gurl.h"
+
+namespace prerender {
+
+// PrerenderHistograms is responsible for recording all prerender specific
+// histograms for PrerenderManager.  It keeps track of the type of prerender
+// currently underway (based on the PrerenderOrigin of the most recent
+// prerenders, and any experiments detected).
+// PrerenderHistograms does not necessarily record all histograms related to
+// prerendering, only the ones in the context of PrerenderManager.
+class PrerenderHistograms {
+ public:
+  // Owned by a PrerenderManager object for the lifetime of the
+  // PrerenderManager.
+  PrerenderHistograms();
+
+  // Records the perceived page load time for a page - effectively the time from
+  // when the user navigates to a page to when it finishes loading.  The actual
+  // load may have started prior to navigation due to prerender hints.
+  void RecordPerceivedPageLoadTime(base::TimeDelta perceived_page_load_time,
+                                   bool was_prerender) const;
+
+  // Records the time from when a page starts prerendering to when the user
+  // navigates to it. This must be called on the UI thread.
+  void RecordTimeUntilUsed(base::TimeDelta time_until_used,
+                           base::TimeDelta max_age) const;
+
+  // Record a PerSessionCount data point.
+  void RecordPerSessionCount(int count) const;
+
+  // Record time between two prerender requests.
+  void RecordTimeBetweenPrerenderRequests(base::TimeDelta time) const;
+
+  // Record a final status of a prerendered page in a histogram.
+  void RecordFinalStatus(Origin origin,
+                         uint8 experiment_id,
+                         FinalStatus final_status) const;
+
+
+  // To be called when a new prerender is added.
+  void RecordPrerender(Origin origin, const GURL& url);
+
+ private:
+  base::TimeTicks GetCurrentTimeTicks() const;
+
+  // Returns whether the PrerenderManager is currently within the prerender
+  // window - effectively, up to 30 seconds after a prerender tag has been
+  // observed.
+  bool WithinWindow() const;
+
+  // Returns the histogram name for the current window.
+  std::string GetDefaultHistogramName(const std::string& name) const;
+  // Returns the current experiment.
+  uint8 GetCurrentExperimentId() const;
+  // Returns the current origin.
+  Origin GetCurrentOrigin() const;
+  // Returns whether or not there is currently an origin/experiment wash.
+  bool IsOriginExperimentWash() const;
+
+  // An integer indicating a Prerendering Experiment being currently conducted.
+  // (The last experiment ID seen).
+  uint8 last_experiment_id_;
+
+  // Origin of the last prerender seen.
+  Origin last_origin_;
+
+  // A boolean indicating that we have recently encountered a combination of
+  // different experiments and origins, making an attribution of PPLT's to
+  // experiments / origins impossible.
+  bool origin_experiment_wash_;
+
+  // The time when we last saw a prerender request coming from a renderer.
+  // This is used to record perceived PLT's for a certain amount of time
+  // from the point that we last saw a <link rel=prerender> tag.
+  base::TimeTicks last_prerender_seen_time_;
+
+  DISALLOW_COPY_AND_ASSIGN(PrerenderHistograms);
+};
+
+}  // namespace prerender
+
+#endif  // CHROME_BROWSER_PRERENDER_PRERENDER_HISTOGRAMS_H_