Fix some issues found looking at the code....

base/histogram.h

 // Copyright (c) 2006-2008 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.
 
 // Histogram is an object that aggregates statistics, and can summarize them in
 // various forms, including ASCII graphical, HTML, and numerically (as a
 // vector of numbers corresponding to each of the aggregating buckets).
 
 // It supports calls to accumulate either time intervals (which are processed
 // as integral number of milliseconds), or arbitrary integral units.
@@ skipping 175 matching lines @@
     // without shared memory at some point.
     int64 sum_;         // sum of samples.
     int64 square_sum_;  // sum of squares of samples.
   };
   //----------------------------------------------------------------------------
 
   Histogram(const wchar_t* name, Sample minimum,
             Sample maximum, size_t bucket_count);
   Histogram(const wchar_t* name, TimeDelta minimum,
             TimeDelta maximum, size_t bucket_count);
-  ~Histogram();
+  virtual ~Histogram();
 
   // Hooks to override stats counter methods.  This ensures that we gather all
   // input the stats counter sees.
   virtual void Add(int value);
 
   // The following methods provide a graphical histogram displays.
   void WriteHTMLGraph(std::string* output) const;
   void WriteAscii(bool graph_it, const std::string& newline,
                   std::string* output) const;
 
@@ skipping 229 matching lines @@
   static Lock* lock_;
 
   // Dump all known histograms to log.
   static bool dump_on_exit_;
 
   DISALLOW_EVIL_CONSTRUCTORS(StatisticsRecorder);
 };
 
 #endif  // BASE_HISTOGRAM_H__