Increase prerender max-age limit to 30 seconds from 20 seconds.

chrome/browser/prerender/prerender_manager.h

 // Copyright (c) 2011 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 <map>
@@ skipping 194 matching lines @@
 
   // Set of TabContents which would be displaying a prerendered page
   // (for the control group).
   base::hash_set<TabContents*> would_be_prerendered_tc_set_;
 
   // Map of child/route id pairs to pending prerender data.
   typedef std::map<std::pair<int, int>, std::vector<PendingContentsData> >
       PendingPrerenderList;
   PendingPrerenderList pending_prerender_list_;
 
-  // Default maximum permitted elements to prerender.
-  static const unsigned int kDefaultMaxPrerenderElements = 1;
-
-  // Default maximum age a prerendered element may have, in seconds.
-  static const int kDefaultMaxPrerenderAgeSeconds = 20;
-
-  // Time window for which we will record windowed PLT's from the last
-  // observed link rel=prefetch tag.
-  static const int kWindowDurationSeconds = 30;
-
-  // Time interval at which periodic cleanups are performed.
-  static const int kPeriodicCleanupIntervalMs = 1000;
-
-  // Time interval before a new prerender is allowed.
-  static const int kMinTimeBetweenPrerendersMs = 500;
-
   scoped_ptr<PrerenderContents::Factory> prerender_contents_factory_;
 
   static PrerenderManagerMode mode_;
 
   // The time when we last saw a prefetch request coming from a renderer.
   // This is used to record perceived PLT's for a certain amount of time
   // from the point that we last saw a <link rel=prefetch> tag.
   // This static variable should only be modified on the UI thread.
   static base::TimeTicks last_prefetch_seen_time_;
 
   // A count of how many prerenders we do per session. Initialized to 0 then
   // incremented and emitted to a histogram on each successful prerender.
   static int prerenders_per_session_count_;
 
   // RepeatingTimer to perform periodic cleanups of pending prerendered
   // pages.
   base::RepeatingTimer<PrerenderManager> repeating_timer_;
 
   // Track time of last prerender to limit prerender spam.
   base::TimeTicks last_prerender_start_time_;
 
   DISALLOW_COPY_AND_ASSIGN(PrerenderManager);
 };
 
 }  // prerender
 
 #endif  // CHROME_BROWSER_PRERENDER_PRERENDER_MANAGER_H_