Fix overflow when logging MaxInt32 to a sparse histogram.

base/metrics/persistent_sample_map_unittest.cc

Index: base/metrics/persistent_sample_map_unittest.cc
diff --git a/base/metrics/persistent_sample_map_unittest.cc b/base/metrics/persistent_sample_map_unittest.cc
index d50ab997b2539d16b3e6ab1aa61c968b00a2e602..933734bd91d8d264f23eb5c3246937d1bf500b4c 100644
--- a/base/metrics/persistent_sample_map_unittest.cc
+++ b/base/metrics/persistent_sample_map_unittest.cc
@@ -164,7 +164,7 @@ TEST(PersistentSampleMapIteratorTest, IterateTest) {
   std::unique_ptr<SampleCountIterator> it = samples.Iterator();
 
   HistogramBase::Sample min;
-  HistogramBase::Sample max;
+  int64_t max;
   HistogramBase::Count count;
 
   it->Get(&min, &max, &count);
@@ -214,7 +214,7 @@ TEST(PersistentSampleMapIteratorTest, SkipEmptyRanges) {
   EXPECT_FALSE(it->Done());
 
   HistogramBase::Sample min;
-  HistogramBase::Sample max;
+  int64_t max;
   HistogramBase::Count count;
 
   it->Get(&min, &max, &count);
@@ -245,7 +245,7 @@ TEST(PersistentSampleMapIteratorDeathTest, IterateDoneTest) {
   EXPECT_TRUE(it->Done());
 
   HistogramBase::Sample min;
-  HistogramBase::Sample max;
+  int64_t max;
   HistogramBase::Count count;
   EXPECT_DCHECK_DEATH(it->Get(&min, &max, &count));