Prerender: Remove PerceivedPLT histograms

chrome/browser/prerender/prerender_histograms.h

Index: chrome/browser/prerender/prerender_histograms.h
diff --git a/chrome/browser/prerender/prerender_histograms.h b/chrome/browser/prerender/prerender_histograms.h
index 71bff438758ac90e03a948094b9de17a19b66c51..3fda4bee4bd05b163d6e14f668a559a2b16b4013 100644
--- a/chrome/browser/prerender/prerender_histograms.h
+++ b/chrome/browser/prerender/prerender_histograms.h
@@ -28,43 +28,34 @@ enum NavigationType {
   NAVIGATION_TYPE_PRERENDERED,
 };
 
-// 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.
+// Records histograms for PrerenderManager.
+//
+// A few histograms are dynamically constructed to avoid binary size bloat from
+// histogram_macros.h. Such histograms require careful handling:
+// 1. slow - make sure only rare events are recorded this way, a handful of such
+//    events per page load should be OK
+// 2. may lead to small sporadic memory leaks in Histogram::Factory::Build() -
+//    ensuring that they are recorded from the same thread is sufficient
+//
+// Besides thread checking this class is stateless, all public methods are
+// const.
 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(Origin origin,
-                                   base::TimeDelta perceived_page_load_time,
-                                   NavigationType navigation_type,
-                                   const GURL& url);
-
   // Record that a first contentful paint occured, and whether we were able to
   // successfuly record the perceived FCP.
   void RecordPerceivedFirstContentfulPaintStatus(Origin origin,
                                                  bool successful,
-                                                 bool was_hidden);
+                                                 bool was_hidden) const;
 
   // Records, in a histogram, the percentage of the page load time that had
   // elapsed by the time it is swapped in.  Values outside of [0, 1.0] are
   // invalid and ignored.
   void RecordPercentLoadDoneAtSwapin(Origin origin, double fraction) const;
 
-  // Records the actual pageload time of a prerender that has not been swapped
-  // in yet, but finished loading.
-  void RecordPageLoadTimeNotSwappedIn(Origin origin,
-                                      base::TimeDelta page_load_time,
-                                      const GURL& url) 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(Origin origin,
@@ -85,16 +76,9 @@ class PrerenderHistograms {
   // Record a final status of a prerendered page in a histogram.
   void RecordFinalStatus(Origin origin, FinalStatus final_status) const;
 
-  // To be called when a new prerender is added.
-  void RecordPrerender();
-
   // To be called when a new prerender is started.
   void RecordPrerenderStarted(Origin origin) const;
 
-  // To be called when we know how many prerenders are running after starting
-  // a prerender.
-  void RecordConcurrency(size_t prerender_count) const;
-
   // Called when we swap in a prerender.
   void RecordUsedPrerender(Origin origin) const;
 
@@ -129,34 +113,14 @@ class PrerenderHistograms {
   // advance of navigation start). One of several histograms is used, depending
   // on whether this URL could have been prefetched before the navigation
   // leading to the paint.
-  void RecordPrefetchFirstContentfulPaintTime(Origin origin,
-                                              bool is_no_store,
-                                              bool was_hidden,
-                                              base::TimeDelta time,
-                                              base::TimeDelta prefetch_age);
+  void RecordPrefetchFirstContentfulPaintTime(
+      Origin origin,
+      bool is_no_store,
+      bool was_hidden,
+      base::TimeDelta time,
+      base::TimeDelta prefetch_age) const;
 
  private:
-  base::TimeTicks GetCurrentTimeTicks() const;
-
-  // Returns the time elapsed since the last prerender happened.
-  base::TimeDelta GetTimeSinceLastPrerender() 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;
-
-  // 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_;
-
-  // Indicates whether we have recorded page load events after the most
-  // recent prerender.  These must be initialized to true, so that we don't
-  // start recording events before the first prerender occurs.
-  bool seen_any_pageload_;
-  bool seen_pageload_started_after_prerender_;
-
   base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(PrerenderHistograms);