Fix overflow when logging MaxInt32 to a sparse histogram.

base/metrics/sparse_histogram_unittest.cc

 // Copyright (c) 2012 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 "base/metrics/sparse_histogram.h"
 
 #include <memory>
 #include <string>
 
 #include "base/metrics/histogram_base.h"
@@ skipping 309 matching lines @@
     histogram->Add(i & 127);
   TimeDelta add_ticks = TimeTicks::Now() - add_start;
   int64_t add_ms = add_ticks.InMilliseconds();
 
   VLOG(1) << kTestAddCount << " histogram adds took " << add_ms
           << "ms or about "
           << (add_ms * 1000000) / kTestAddCount
           << "ns each.";
 }
 
+TEST_P(SparseHistogramTest, ExtremeValues) {
+  static const struct {
+    Histogram::Sample sample;
+    int64_t expected_max;
+  } cases[] = {
+      // Note: We use -2147483647 - 1 rather than -2147483648 because the later
+      // is interpreted as - operator applied to 2147483648 and the latter can't
+      // be represented as an int32 and causes a warning.
+      {-2147483647 - 1, -2147483647LL},
+      {0, 1},
+      {2147483647, 2147483648LL},
+  };
+
+  for (size_t i = 0; i < arraysize(cases); ++i) {
+    HistogramBase* histogram =
+        SparseHistogram::FactoryGet(StringPrintf("ExtremeValues_%zu", i),
+                                    HistogramBase::kUmaTargetedHistogramFlag);
+    histogram->Add(cases[i].sample);
+
+    std::unique_ptr<HistogramSamples> snapshot = histogram->SnapshotSamples();
+    std::unique_ptr<SampleCountIterator> it = snapshot->Iterator();
+    ASSERT_FALSE(it->Done());
+
+    base::Histogram::Sample min;
+    int64_t max;
+    base::Histogram::Count count;
+    it->Get(&min, &max, &count);
+
+    EXPECT_EQ(1, count);
+    EXPECT_EQ(cases[i].sample, min);
+    EXPECT_EQ(cases[i].expected_max, max);
+
+    it->Next();
+    EXPECT_TRUE(it->Done());
+  }
+}
+
 }  // namespace base