This adds periodic OOM score adjustment, based on the last access time

chrome/browser/tab_contents/tab_contents.h

 // Copyright (c) 2010 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_TAB_CONTENTS_TAB_CONTENTS_H_
 #define CHROME_BROWSER_TAB_CONTENTS_TAB_CONTENTS_H_
 #pragma once
 
 #include "build/build_config.h"
 
@@ skipping 300 matching lines @@
   // us not to store focus when a tab is being closed.
   bool is_being_destroyed() const { return is_being_destroyed_; }
 
   // Convenience method for notifying the delegate of a navigation state
   // change. See TabContentsDelegate.
   void NotifyNavigationStateChanged(unsigned changed_flags);
 
   // Invoked when the tab contents becomes selected. If you override, be sure
   // and invoke super's implementation.
   virtual void DidBecomeSelected();
+  base::TimeTicks last_selected_time() const {
+    return last_selected_time_;
+  }
 
   // Invoked when the tab contents becomes hidden.
   // NOTE: If you override this, call the superclass version too!
   virtual void WasHidden();
 
   // Activates this contents within its containing window, bringing that window
   // to the foreground if necessary.
   void Activate();
 
   // Deactivates this contents by deactivating its containing window.
@@ skipping 915 matching lines @@
   // If this tab was created from a renderer using window.open, this will be
   // non-NULL and represent the DOMUI of the opening renderer.
   DOMUITypeID opener_dom_ui_type_;
 
   // The time that we started to create the new tab page.
   base::TimeTicks new_tab_start_time_;
 
   // The time that we started to close the tab.
   base::TimeTicks tab_close_start_time_;
 
+  // The time that this tab was last selected.
+  base::TimeTicks last_selected_time_;
+
   // Information about the language the page is in and has been translated to.
   LanguageState language_state_;
 
   // See description above setter.
   bool closed_by_user_gesture_;
 
   // See description in RenderViewHostDelegate::SetDisplayingPDFContent.
   bool displaying_pdf_content_;
 
   scoped_ptr<MatchPreview> match_preview_;
 
   // ---------------------------------------------------------------------------
 
   DISALLOW_COPY_AND_ASSIGN(TabContents);
 };
 
 #endif  // CHROME_BROWSER_TAB_CONTENTS_TAB_CONTENTS_H_