Fix overflow when logging MaxInt32 to a sparse histogram.

components/metrics/histogram_encoder.cc

 // Copyright 2014 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 "components/metrics/histogram_encoder.h"
 
 #include <memory>
 #include <string>
 
 #include "base/metrics/histogram.h"
@@ skipping 13 matching lines @@
   // We will ignore the MAX_INT/infinite value in the last element of range[].
 
   HistogramEventProto* histogram_proto = uma_proto->add_histogram_event();
   histogram_proto->set_name_hash(base::HashMetricName(histogram_name));
   if (snapshot.sum() != 0)
     histogram_proto->set_sum(snapshot.sum());
 
   for (std::unique_ptr<SampleCountIterator> it = snapshot.Iterator();
        !it->Done(); it->Next()) {
     base::Histogram::Sample min;
-    base::Histogram::Sample max;
+    int64_t max;
     base::Histogram::Count count;
     it->Get(&min, &max, &count);
     HistogramEventProto::Bucket* bucket = histogram_proto->add_bucket();
     bucket->set_min(min);
     bucket->set_max(max);
     // Note: The default for count is 1 in the proto, so omit it in that case.
     if (count != 1)
       bucket->set_count(count);
   }
 
   // Omit fields to save space (see rules in histogram_event.proto comments).
   for (int i = 0; i < histogram_proto->bucket_size(); ++i) {
     HistogramEventProto::Bucket* bucket = histogram_proto->mutable_bucket(i);
     if (i + 1 < histogram_proto->bucket_size() &&
         bucket->max() == histogram_proto->bucket(i + 1).min()) {
       bucket->clear_max();
     } else if (bucket->max() == bucket->min() + 1) {
       bucket->clear_min();
     }
   }
 }
 
 }  // namespace metrics