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

chrome/browser/sessions/session_restore_delegate.cc

Index: chrome/browser/sessions/session_restore_delegate.cc
diff --git a/chrome/browser/sessions/session_restore_delegate.cc b/chrome/browser/sessions/session_restore_delegate.cc
index 9d5c3122709459dff1f353967f51ca45e44af392..52564f97adf048836da07c485e0ff02248b2d72b 100644
--- a/chrome/browser/sessions/session_restore_delegate.cc
+++ b/chrome/browser/sessions/session_restore_delegate.cc
@@ -57,7 +57,11 @@ bool SessionRestoreDelegate::RestoredTab::operator<(
   // 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;
 }