Fix overflow bug in histogram sample data structures

base/metrics/sample_map.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_map.h"
 
 #include "base/logging.h"
 
 namespace base {
 
 typedef HistogramBase::Count Count;
 typedef HistogramBase::Sample Sample;
 
 SampleMap::SampleMap() : SampleMap(0) {}
 
 SampleMap::SampleMap(uint64_t id) : HistogramSamples(id) {}
 
 SampleMap::~SampleMap() {}
 
 void SampleMap::Accumulate(Sample value, Count count) {
   sample_counts_[value] += count;
-  IncreaseSum(count * value);
+  IncreaseSum(static_cast<int64_t>(count) * value);
   IncreaseRedundantCount(count);
 }
 
 Count SampleMap::GetCount(Sample value) const {
   std::map<Sample, Count>::const_iterator it = sample_counts_.find(value);
   if (it == sample_counts_.end())
     return 0;
   return it->second;
 }
 
@@ skipping 52 matching lines @@
     *count = iter_->second;
 }
 
 void SampleMapIterator::SkipEmptyBuckets() {
   while (!Done() && iter_->second == 0) {
     ++iter_;
   }
 }
 
 }  // namespace base