Fix overflow when logging MaxInt32 to a sparse histogram.

base/metrics/sparse_histogram.cc

Index: base/metrics/sparse_histogram.cc
diff --git a/base/metrics/sparse_histogram.cc b/base/metrics/sparse_histogram.cc
index 415d7f943024a84965933cfb39af4024fd334ea6..916dcd5739ef845e824102b8f648dd43c62aeed8 100644
--- a/base/metrics/sparse_histogram.cc
+++ b/base/metrics/sparse_histogram.cc
@@ -243,7 +243,7 @@ void SparseHistogram::WriteAsciiImpl(bool graph_it,
   std::unique_ptr<SampleCountIterator> it = snapshot->Iterator();
   while (!it->Done()) {
     Sample min;
-    Sample max;
+    int64_t max;
     Count count;
     it->Get(&min, &max, &count);
     if (min > largest_sample)
@@ -258,7 +258,7 @@ void SparseHistogram::WriteAsciiImpl(bool graph_it,
   it = snapshot->Iterator();
   while (!it->Done()) {
     Sample min;
-    Sample max;
+    int64_t max;
     Count count;
     it->Get(&min, &max, &count);