Fix overflow bug in histogram sample data structures

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"
 
 namespace base {
@@ skipping 25 matching lines @@
   CHECK_LE(bucket_ranges_->bucket_count(), counts_size_);
   CHECK_GE(bucket_ranges_->bucket_count(), 1u);
 }
 
 SampleVector::~SampleVector() {}
 
 void SampleVector::Accumulate(Sample value, Count count) {
   size_t bucket_index = GetBucketIndex(value);
   subtle::NoBarrier_Store(&counts_[bucket_index],
       subtle::NoBarrier_Load(&counts_[bucket_index]) + count);
-  IncreaseSum(count * value);
+  IncreaseSum(static_cast<int64_t>(count) * value);
   IncreaseRedundantCount(count);
 }
 
 Count SampleVector::GetCount(Sample value) const {
   size_t bucket_index = GetBucketIndex(value);
   return subtle::NoBarrier_Load(&counts_[bucket_index]);
 }
 
 Count SampleVector::TotalCount() const {
   Count count = 0;
@@ skipping 130 matching lines @@
     return;
 
   while (index_ < counts_size_) {
     if (subtle::NoBarrier_Load(&counts_[index_]) != 0)
       return;
     index_++;
   }
 }
 
 }  // namespace base