Fix overflow when logging MaxInt32 to a sparse histogram.

base/metrics/sample_map_unittest.cc

Index: base/metrics/sample_map_unittest.cc
diff --git a/base/metrics/sample_map_unittest.cc b/base/metrics/sample_map_unittest.cc
index 91a9dcf40f83d61506cf7c50b7246c48df9373ee..6e6da2b3d24cdb8220fa32c16b92cc1470a37f65 100644
--- a/base/metrics/sample_map_unittest.cc
+++ b/base/metrics/sample_map_unittest.cc
@@ -81,7 +81,7 @@ TEST(SampleMapIteratorTest, 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);
@@ -125,7 +125,7 @@ TEST(SampleMapIteratorTest, SkipEmptyRanges) {
   EXPECT_FALSE(it->Done());
 
   HistogramBase::Sample min;
-  HistogramBase::Sample max;
+  int64_t max;
   HistogramBase::Count count;
 
   it->Get(&min, &max, &count);
@@ -153,7 +153,7 @@ TEST(SampleMapIteratorDeathTest, 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));