Removes some dead database code

chrome/browser/history/page_usage_data.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_HISTORY_PAGE_USAGE_DATA_H__
 #define CHROME_BROWSER_HISTORY_PAGE_USAGE_DATA_H__
 
 #include "base/strings/string16.h"
-#include "base/time/time.h"
 #include "chrome/browser/history/history_types.h"
 #include "url/gurl.h"
 
 class SkBitmap;
 
 /////////////////////////////////////////////////////////////////////////////
 //
 // PageUsageData
 //
 // A per domain usage data structure to compute and manage most visited
@@ skipping 30 matching lines @@
   }
 
   void SetScore(double v) {
     score_ = v;
   }
 
   double GetScore() const {
     return score_;
   }
 
-  void SetDuration(base::TimeDelta duration) {
-    duration_ = duration;
-  }
-
-  base::TimeDelta duration() const {
-    return duration_;
-  }
-
   // Sort predicate to sort instances by score (high to low)
   static bool Predicate(const PageUsageData* dud1, const PageUsageData* dud2);
 
  private:
   history::SegmentID id_;
   GURL url_;
   base::string16 title_;
 
   double score_;
-
-  // Duration is only set by QuerySegmentDurationSince().
-  base::TimeDelta duration_;
 };
 
 #endif  // CHROME_BROWSER_HISTORY_PAGE_USAGE_DATA_H__