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

chrome/browser/sessions/tab_restore_service.h

 // Copyright 2012 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_SESSIONS_TAB_RESTORE_SERVICE_H_
 #define CHROME_BROWSER_SESSIONS_TAB_RESTORE_SERVICE_H_
 
 #include <list>
 #include <string>
 #include <vector>
@@ skipping 87 matching lines @@
     bool pinned;
 
     // If non-empty gives the id of the extension for the tab.
     std::string extension_app_id;
 
     // The associated session storage namespace (if any).
     scoped_refptr<content::SessionStorageNamespace> session_storage_namespace;
 
     // The user agent override used for the tab's navigations (if applicable).
     std::string user_agent_override;
+
+    // Timestamp of the last time the tab was active.
+    base::TimeTicks last_active_time;
   };
 
   // Represents a previously open window.
   struct Window : public Entry {
     Window();
     ~Window() override;
 
     // The tabs that comprised the window, in order.
     std::vector<Tab> tabs;
 
@@ skipping 65 matching lines @@
   virtual void LoadTabsFromLastSession() = 0;
 
   // Returns true if the tab entries have been loaded.
   virtual bool IsLoaded() const = 0;
 
   // Deletes the last session.
   virtual void DeleteLastSession() = 0;
 };
 
 #endif  // CHROME_BROWSER_SESSIONS_TAB_RESTORE_SERVICE_H_