Fix overflow bug in histogram sample data structures

base/metrics/sample_vector_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/sample_vector.h"
 
 #include <limits.h>
 #include <stddef.h>
 
 #include <vector>
@@ skipping 26 matching lines @@
   EXPECT_EQ(samples.TotalCount(), samples.redundant_count());
 
   samples.Accumulate(5, -100);
   EXPECT_EQ(100, samples.GetCountAtIndex(1));
 
   EXPECT_EQ(100, samples.sum());
   EXPECT_EQ(0, samples.redundant_count());
   EXPECT_EQ(samples.TotalCount(), samples.redundant_count());
 }
 
+TEST(SampleVectorTest, Accumulate_LargeValuesDontOverflow) {
+  // Custom buckets: [1, 250000000) [250000000, 500000000)
+  BucketRanges ranges(3);
+  ranges.set_range(0, 1);
+  ranges.set_range(1, 250000000);
+  ranges.set_range(2, 500000000);
+  SampleVector samples(1, &ranges);
+
+  samples.Accumulate(240000000, 200);
+  samples.Accumulate(249999999, -300);
+  EXPECT_EQ(-100, samples.GetCountAtIndex(0));
+
+  samples.Accumulate(250000000, 200);
+  EXPECT_EQ(200, samples.GetCountAtIndex(1));
+
+  EXPECT_EQ(23000000300LL, samples.sum());
+  EXPECT_EQ(100, samples.redundant_count());
+  EXPECT_EQ(samples.TotalCount(), samples.redundant_count());
+
+  samples.Accumulate(250000000, -100);
+  EXPECT_EQ(100, samples.GetCountAtIndex(1));
+
+  EXPECT_EQ(-1999999700LL, samples.sum());
+  EXPECT_EQ(0, samples.redundant_count());
+  EXPECT_EQ(samples.TotalCount(), samples.redundant_count());
+}
+
 TEST(SampleVectorTest, AddSubtractTest) {
   // Custom buckets: [0, 1) [1, 2) [2, 3) [3, INT_MAX)
   BucketRanges ranges(5);
   ranges.set_range(0, 0);
   ranges.set_range(1, 1);
   ranges.set_range(2, 2);
   ranges.set_range(3, 3);
   ranges.set_range(4, INT_MAX);
 
   SampleVector samples1(1, &ranges);
@@ skipping 201 matching lines @@
   samples.Accumulate(2, 100);
   it = samples.Iterator();
   EXPECT_FALSE(it->Done());
 }
 
 #endif
 // (!defined(NDEBUG) || defined(DCHECK_ALWAYS_ON)) && GTEST_HAS_DEATH_TEST
 
 }  // namespace
 }  // namespace base