Fix overflow when logging MaxInt32 to a sparse histogram.

base/metrics/sample_vector.cc

Index: base/metrics/sample_vector.cc
diff --git a/base/metrics/sample_vector.cc b/base/metrics/sample_vector.cc
index b55449d245be4089b39973c2f3c12414865433ad..c9b7a40ee77e04b3d2ddbed16987c5630032052e 100644
--- a/base/metrics/sample_vector.cc
+++ b/base/metrics/sample_vector.cc
@@ -132,7 +132,7 @@ bool SampleVectorBase::AddSubtractImpl(SampleCountIterator* iter,
 
   // Get the first value and its index.
   HistogramBase::Sample min;
-  HistogramBase::Sample max;
+  int64_t max;
   HistogramBase::Count count;
   iter->Get(&min, &max, &count);
   size_t dest_index = GetBucketIndex(min);
@@ -392,13 +392,13 @@ void SampleVectorIterator::Next() {
 }
 
 void SampleVectorIterator::Get(HistogramBase::Sample* min,
-                               HistogramBase::Sample* max,
+                               int64_t* max,
                                HistogramBase::Count* count) const {
   DCHECK(!Done());
   if (min != NULL)
     *min = bucket_ranges_->range(index_);
   if (max != NULL)
-    *max = bucket_ranges_->range(index_ + 1);
+    *max = static_cast<int64_t>(bucket_ranges_->range(index_ + 1));
   if (count != NULL)
     *count = subtle::NoBarrier_Load(&counts_[index_]);
 }