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

chrome/browser/sessions/session_restore_delegate.cc

 // Copyright 2015 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.
 
 #include "chrome/browser/sessions/session_restore_delegate.h"
 
 #include "base/metrics/field_trial.h"
 #include "chrome/browser/sessions/session_restore_stats_collector.h"
 #include "chrome/browser/sessions/tab_loader.h"
 #include "chrome/common/url_constants.h"
@@ skipping 39 matching lines @@
   // Tab with internal web UI like NTP or Settings are good choices to
   // defer loading.
   if (is_internal_page_ != right.is_internal_page_)
     return !is_internal_page_;
   // Pinned tabs should be loaded first.
   if (is_pinned_ != right.is_pinned_)
     return is_pinned_;
   // Apps should be loaded before normal tabs.
   if (is_app_ != right.is_app_)
     return is_app_;
-  // TODO(georgesak): Add criterion based on recency.
+  // Restore using MRU. Behind an experiment for now.
+  if (SessionRestore::GetSmartRestoreMode() ==
+      SessionRestore::SMART_RESTORE_MODE_MRU)
+    return contents_->GetLastActiveTime() >
+           right.contents_->GetLastActiveTime();
   return false;
 }
 
 // static
 void SessionRestoreDelegate::RestoreTabs(
     const std::vector<RestoredTab>& tabs,
     const base::TimeTicks& restore_started) {
   // This experiment allows us to have comparative numbers for session restore
   // metrics. It will be removed once those numbers are obtained.
   // TODO(georgesak): Remove this experiment when stats are collected.
   base::FieldTrial* trial =
       base::FieldTrialList::Find("IntelligentSessionRestore");
   if (!trial || trial->group_name() != "DontRestoreBackgroundTabs") {
     SessionRestoreStatsCollector::TrackTabs(tabs, restore_started);
     TabLoader::RestoreTabs(tabs, restore_started);
   } else {
     SessionRestoreStatsCollector::TrackActiveTabs(tabs, restore_started);
     for (auto& restored_tab : tabs) {
       if (!restored_tab.is_active()) {
         favicon::ContentFaviconDriver* favicon_driver =
             favicon::ContentFaviconDriver::FromWebContents(
                 restored_tab.contents());
         favicon_driver->FetchFavicon(favicon_driver->GetActiveURL());
       }
     }
   }
 }