Add SampleMap and use it in SparseHistogram

base/metrics/sample_vector.cc

 // 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.
 
 #include "base/metrics/sample_vector.h"
 
 #include "base/logging.h"
 #include "base/metrics/bucket_ranges.h"
 
 using std::vector;
@@ skipping 99 matching lines @@
 
 SampleVectorIterator::SampleVectorIterator(const vector<Count>* counts,
                                            const BucketRanges* bucket_ranges)
     : counts_(counts),
       bucket_ranges_(bucket_ranges),
       index_(0) {
   CHECK_GT(bucket_ranges_->size(), counts_->size());
   SkipEmptyBuckets();
 }
 
+SampleVectorIterator::~SampleVectorIterator() {}
+
 bool SampleVectorIterator::Done() const {
   return index_ >= counts_->size();
 }
 
 void SampleVectorIterator::Next() {
   DCHECK(!Done());
   index_++;
   SkipEmptyBuckets();
 }
 
@@ skipping 21 matching lines @@
     return;
 
   while (index_ < counts_->size()) {
     if ((*counts_)[index_] != 0)
       return;
     index_++;
   }
 }
 
 }  // namespace base