[Prerender] first contentful paint histograms.

chrome/browser/prerender/prerender_manager.h

Index: chrome/browser/prerender/prerender_manager.h
diff --git a/chrome/browser/prerender/prerender_manager.h b/chrome/browser/prerender/prerender_manager.h
index ee4bf7f2ff1fb9cb782c31ddd4a59ef4c8c6da70..3bd28deae260ce7f60eafd4cf0512f71210f7b1d 100644
--- a/chrome/browser/prerender/prerender_manager.h
+++ b/chrome/browser/prerender/prerender_manager.h
@@ -72,6 +72,13 @@ class PrerenderHandle;
 class PrerenderHistory;
 class PrerenderLocalPredictor;
 
+// Observer interface for PrerenderManager events.
+class PrerenderManagerObserver {
+ public:
+  // Called from the UI thread.
+  virtual void OnFirstContentfulPaint() = 0;
+};
+
 // PrerenderManager is responsible for initiating and keeping prerendered
 // views of web pages. All methods must be called on the UI thread unless
 // indicated otherwise.
@@ -219,13 +226,21 @@ class PrerenderManager : public content::NotificationObserver,
                                    bool is_main_resource,
                                    int redirect_count);
 
-  // Records the time to first contentful paint.
-  // Must not be called for prefetch loads (which are never rendered anyway).
-  // |is_no_store| must be true if the main resource has a "no-store" cache
-  // control HTTP header.
-  void RecordFirstContentfulPaint(const GURL& url,
-                                  bool is_no_store,
-                                  base::TimeDelta time);
+  // Records the time to first contentful paint for loads that previously had a
+  // no state prefetch load.  Must not be called for prefetch loads themselves
+  // (which are never rendered anyway).  |is_no_store| must be true if the main
+  // resource has a "no-store" cache control HTTP header.
+  void RecordNoStateFirstContentfulPaint(const GURL& url,
+                                         bool is_no_store,
+                                         base::TimeDelta time);
+
+  // Records the perceived first contentful paint time for a prerendered page,
+  // analogous to |RecordPerceivedPageLoadTime|. The FCP ticks is in absolute
+  // time; this has the disadvantage that the histogram will mix browser and
+  // renderer ticks, but there seems to be no way around that.
+  void RecordPerceivedFirstContentfulPaint(content::WebContents* web_contents,
+                                           base::TimeTicks ticks,
+                                           bool was_hidden);
 
   static PrerenderManagerMode GetMode();
   static void SetMode(PrerenderManagerMode mode);
@@ -329,6 +344,16 @@ class PrerenderManager : public content::NotificationObserver,
   void SetTickClockForTesting(
       std::unique_ptr<base::SimpleTestTickClock> tick_clock);
 
+  void DisablePageLoadMetricsObserverForTesting() {
+    page_load_metric_observer_disabled_ = true;
+  }
+
+  bool PageLoadMetricsObserverDisabledForTesting() const {
+    return page_load_metric_observer_disabled_;
+  }
+
+  void AddObserver(std::unique_ptr<PrerenderManagerObserver> observer);
+
   // Notification that a prerender has completed and its bytes should be
   // recorded.
   void RecordNetworkBytes(Origin origin, bool used, int64_t prerender_bytes);
@@ -610,6 +635,10 @@ class PrerenderManager : public content::NotificationObserver,
   std::unique_ptr<base::Clock> clock_;
   std::unique_ptr<base::TickClock> tick_clock_;
 
+  bool page_load_metric_observer_disabled_;
+
+  std::vector<std::unique_ptr<PrerenderManagerObserver>> observers_;
+
   base::WeakPtrFactory<PrerenderManager> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(PrerenderManager);