[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 15 matching lines @@
   for (size_t i = 0; i < arraysize(kReloadableUrlPrefixes); ++i) {
     if (!strncmp(url.spec().c_str(), kReloadableUrlPrefixes[i],
                  strlen(kReloadableUrlPrefixes[i])))
       return true;
   }
   return false;
 }
 
 }  // namespace
 
-SessionRestoreDelegate::RestoredTab::RestoredTab(content::WebContents* contents,
-                                                 bool is_active,
-                                                 bool is_app,
-                                                 bool is_pinned)
+SessionRestoreDelegate::RestoredTab::RestoredTab(
+    content::WebContents* contents,
+    bool is_active,
+    bool is_app,
+    bool is_pinned,
+    base::TimeTicks last_activation_time)
     : contents_(contents),
       is_active_(is_active),
       is_app_(is_app),
       is_internal_page_(IsInternalPage(contents->GetLastCommittedURL())),
-      is_pinned_(is_pinned) {
+      is_pinned_(is_pinned),
+      last_activation_time_(last_activation_time) {
 }
 
 bool SessionRestoreDelegate::RestoredTab::operator<(
     const RestoredTab& right) const {
   // 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 last_activation_time_ > right.last_activation_time_;
   return false;
 }
 
 // static
 void SessionRestoreDelegate::RestoreTabs(
     const std::vector<RestoredTab>& tabs,
     const base::TimeTicks& restore_started) {
   SessionRestoreStatsCollector::TrackTabs(tabs, restore_started);
   TabLoader::RestoreTabs(tabs, restore_started);
 }