Add field trial to extend prerender expiration to 5 minutes.

chrome/browser/prerender/prerender_manager.h

 // Copyright (c) 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_PRERENDER_PRERENDER_MANAGER_H_
 #define CHROME_BROWSER_PRERENDER_PRERENDER_MANAGER_H_
 #pragma once
 
 #include <list>
 #include <string>
@@ skipping 51 matching lines @@
                          public base::NonThreadSafe,
                          public ProfileKeyedService {
  public:
   // PrerenderManagerMode is used in a UMA_HISTOGRAM, so please do not
   // add in the middle.
   enum PrerenderManagerMode {
     PRERENDER_MODE_DISABLED,
     PRERENDER_MODE_ENABLED,
     PRERENDER_MODE_EXPERIMENT_CONTROL_GROUP,
     PRERENDER_MODE_EXPERIMENT_PRERENDER_GROUP,
+    PRERENDER_MODE_EXPERIMENT_LONG_TTL_GROUP,
     PRERENDER_MODE_EXPERIMENT_NO_USE_GROUP,
     PRERENDER_MODE_MAX
   };
 
   // One or more of these flags must be passed to ClearData() to specify just
   // what data to clear.  See function declaration for more information.
   enum ClearFlags {
     CLEAR_PRERENDER_CONTENTS = 0x1 << 0,
     CLEAR_PRERENDER_HISTORY = 0x1 << 1,
     CLEAR_MAX = 0x1 << 2
@@ skipping 228 matching lines @@
   // TabContents that have been replaced by prerendered TabContents.
   // Also identifies and kills PrerenderContents that use too much
   // resources.
   void PeriodicCleanup();
 
   // Posts a task to call PeriodicCleanup.  Results in quicker destruction of
   // objects.  If |this| is deleted before the task is run, the task will
   // automatically be cancelled.
   void PostCleanupTask();
 
+  base::TimeDelta GetMaxAge() const;
   bool IsPrerenderElementFresh(const base::Time start) const;
   void DeleteOldEntries();
   virtual base::Time GetCurrentTime() const;
   virtual base::TimeTicks GetCurrentTimeTicks() const;
   virtual PrerenderContents* CreatePrerenderContents(
       const GURL& url,
       const content::Referrer& referrer,
       Origin origin,
       uint8 experiment_id);
 
@@ skipping 121 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(PrerenderManager);
 };
 
 PrerenderManager* FindPrerenderManagerUsingRenderProcessId(
     int render_process_id);
 
 }  // namespace prerender
 
 #endif  // CHROME_BROWSER_PRERENDER_PRERENDER_MANAGER_H_