Update from https://crrev.com/333737

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 1a53ee7f546b38525c8c4b2836fb3649ca74cc38..22ce8e1c8e3ab3a347af2e008ce622bb662cd67d 100644
--- a/base/metrics/sample_map_unittest.cc
+++ b/base/metrics/sample_map_unittest.cc
@@ -2,8 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "base/memory/scoped_ptr.h"
 #include "base/metrics/sample_map.h"
+
+#include "base/memory/scoped_ptr.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
@@ -86,10 +87,43 @@ TEST(SampleMapIteratorTest, IterateTest) {
   EXPECT_EQ(-300, count);
 
   it->Next();
+  EXPECT_TRUE(it->Done());
+}
+
+TEST(SampleMapIteratorTest, SkipEmptyRanges) {
+  SampleMap samples;
+  samples.Accumulate(5, 1);
+  samples.Accumulate(10, 2);
+  samples.Accumulate(15, 3);
+  samples.Accumulate(20, 4);
+  samples.Accumulate(25, 5);
+
+  SampleMap samples2;
+  samples2.Accumulate(5, 1);
+  samples2.Accumulate(20, 4);
+  samples2.Accumulate(25, 5);
+
+  samples.Subtract(samples2);
+
+  scoped_ptr<SampleCountIterator> it = samples.Iterator();
+  EXPECT_FALSE(it->Done());
+
+  HistogramBase::Sample min;
+  HistogramBase::Sample max;
+  HistogramBase::Count count;
+
+  it->Get(&min, &max, &count);
+  EXPECT_EQ(10, min);
+  EXPECT_EQ(11, max);
+  EXPECT_EQ(2, count);
+
+  it->Next();
+  EXPECT_FALSE(it->Done());
+
   it->Get(&min, &max, &count);
-  EXPECT_EQ(5, min);
-  EXPECT_EQ(6, max);
-  EXPECT_EQ(0, count);
+  EXPECT_EQ(15, min);
+  EXPECT_EQ(16, max);
+  EXPECT_EQ(3, count);
 
   it->Next();
   EXPECT_TRUE(it->Done());