[Sessions] Add detailed logging of SessionRestore events.

chrome/browser/sessions/tab_loader.h

Index: chrome/browser/sessions/tab_loader.h
diff --git a/chrome/browser/sessions/tab_loader.h b/chrome/browser/sessions/tab_loader.h
index d40987d59077d2fcf0ce65bc8561d03345df556e..32714e83fcbd4991da934fd707d8c05a6377d55c 100644
--- a/chrome/browser/sessions/tab_loader.h
+++ b/chrome/browser/sessions/tab_loader.h
@@ -21,6 +21,8 @@ class NavigationController;
 class RenderWidgetHost;
 }
 
+class SessionRestoreStatsCollector;
+
 // TabLoader is responsible for loading tabs after session restore has finished
 // creating all the tabs. Tabs are loaded after a previously tab finishes
 // loading or a timeout is reached. If the timeout is reached before a tab
@@ -132,6 +134,11 @@ class TabLoader : public content::NotificationObserver,
   // SessionRestoreImpls reference it.
   scoped_refptr<TabLoader> this_retainer_;
 
+  // The SessionRestoreStatsCollector associated with this TabLoader. This is
+  // explicitly referenced so that it can be notified of deferred tab loads due
+  // to memory pressure.
+  scoped_refptr<SessionRestoreStatsCollector> stats_collector_;
+
   static TabLoader* shared_tab_loader_;
 
   DISALLOW_COPY_AND_ASSIGN(TabLoader);