[Session restore] Add MRU logic to loading of background pages.

chrome/browser/sessions/session_service.h

Index: chrome/browser/sessions/session_service.h
diff --git a/chrome/browser/sessions/session_service.h b/chrome/browser/sessions/session_service.h
index ca409cfe9aede8e262b12d24e15a4fdee8d662bd..4b2d4a37503d98fcb7c5345625d4e9bb0415c048 100644
--- a/chrome/browser/sessions/session_service.h
+++ b/chrome/browser/sessions/session_service.h
@@ -201,6 +201,11 @@ class SessionService : public BaseSessionServiceDelegateImpl,
                             const SessionID& tab_id,
                             const std::string& extension_app_id);
 
+  // Sets the activation time of the tab.
+  void SetActivationTime(const SessionID& window_id,
+                         const SessionID& tab_id,
+                         base::TimeTicks activation_time);
+
   // Callback from GetLastSession.
   // The second parameter is the id of the window that was last active.
   typedef base::Callback<void(ScopedVector<sessions::SessionWindow>,