Clean up base histograms code.

Cleans up some existing style issues as well as switching
to some cleaner C++11 constructs (e.g. new for loops),
and removing using declarations for std:: classes, which
Chromium typically avoids.

BUG=none

Review URL: https://codereview.chromium.org/1158043002

Cr-Commit-Position: refs/heads/master@{#331535}

10 files changed, 86 insertions, 123 deletions

diff --git a/base/metrics/histogram.cc b/base/metrics/histogram.cc
index 42ced3d..1550420 100644
--- a/base/metrics/histogram.cc
+++ b/base/metrics/histogram.cc
@@ -25,15 +25,12 @@
 #include "base/synchronization/lock.h"
 #include "base/values.h"
 
-using std::string;
-using std::vector;
-
 namespace base {
 
 namespace {
 
 bool ReadHistogramArguments(PickleIterator* iter,
-                            string* histogram_name,
+                            std::string* histogram_name,
                             int* flags,
                             int* declared_min,
                             int* declared_max,
@@ -84,7 +81,7 @@ typedef HistogramBase::Sample Sample;
 // static
 const size_t Histogram::kBucketCount_MAX = 16384u;
 
-HistogramBase* Histogram::FactoryGet(const string& name,
+HistogramBase* Histogram::FactoryGet(const std::string& name,
                                      Sample minimum,
                                      Sample maximum,
                                      size_t bucket_count,
@@ -123,7 +120,7 @@ HistogramBase* Histogram::FactoryGet(const string& name,
   return histogram;
 }
 
-HistogramBase* Histogram::FactoryTimeGet(const string& name,
+HistogramBase* Histogram::FactoryTimeGet(const std::string& name,
                                          TimeDelta minimum,
                                          TimeDelta maximum,
                                          size_t bucket_count,
@@ -216,7 +213,7 @@ size_t Histogram::bucket_count() const {
 }
 
 // static
-bool Histogram::InspectConstructionArguments(const string& name,
+bool Histogram::InspectConstructionArguments(const std::string& name,
                                              Sample* minimum,
                                              Sample* maximum,
                                              size_t* bucket_count) {
@@ -280,14 +277,14 @@ bool Histogram::AddSamplesFromPickle(PickleIterator* iter) {
 }
 
 // The following methods provide a graphical histogram display.
-void Histogram::WriteHTMLGraph(string* output) const {
+void Histogram::WriteHTMLGraph(std::string* output) const {
   // TBD(jar) Write a nice HTML bar chart, with divs an mouse-overs etc.
   output->append("<PRE>");
   WriteAsciiImpl(true, "<br>", output);
   output->append("</PRE>");
 }
 
-void Histogram::WriteAscii(string* output) const {
+void Histogram::WriteAscii(std::string* output) const {
   WriteAsciiImpl(true, "\n", output);
 }
 
@@ -301,7 +298,7 @@ bool Histogram::SerializeInfoImpl(Pickle* pickle) const {
       pickle->WriteUInt32(bucket_ranges()->checksum());
 }
 
-Histogram::Histogram(const string& name,
+Histogram::Histogram(const std::string& name,
                      Sample minimum,
                      Sample maximum,
                      const BucketRanges* ranges)
@@ -334,7 +331,7 @@ double Histogram::GetBucketSize(Count current, size_t i) const {
   return current/denominator;
 }
 
-const string Histogram::GetAsciiBucketRange(size_t i) const {
+const std::string Histogram::GetAsciiBucketRange(size_t i) const {
   return GetSimpleAsciiBucketRange(ranges(i));
 }
 
@@ -343,7 +340,7 @@ const string Histogram::GetAsciiBucketRange(size_t i) const {
 
 // static
 HistogramBase* Histogram::DeserializeInfoImpl(PickleIterator* iter) {
-  string histogram_name;
+  std::string histogram_name;
   int flags;
   int declared_min;
   int declared_max;
@@ -373,8 +370,8 @@ scoped_ptr<SampleVector> Histogram::SnapshotSampleVector() const {
 }
 
 void Histogram::WriteAsciiImpl(bool graph_it,
-                               const string& newline,
-                               string* output) const {
+                               const std::string& newline,
+                               std::string* output) const {
   // Get local (stack) copies of all effectively volatile class data so that we
   // are consistent across our output activities.
   scoped_ptr<SampleVector> snapshot = SnapshotSampleVector();
@@ -415,7 +412,7 @@ void Histogram::WriteAsciiImpl(bool graph_it,
     if (!current && !PrintEmptyBucket(i))
       continue;
     remaining -= current;
-    string range = GetAsciiBucketRange(i);
+    std::string range = GetAsciiBucketRange(i);
     output->append(range);
     for (size_t j = 0; range.size() + j < print_width + 1; ++j)
       output->push_back(' ');
@@ -451,7 +448,7 @@ double Histogram::GetPeakBucketSize(const SampleVector& samples) const {
 
 void Histogram::WriteAsciiHeader(const SampleVector& samples,
                                  Count sample_count,
-                                 string* output) const {
+                                 std::string* output) const {
   StringAppendF(output,
                 "Histogram: %s recorded %d samples",
                 histogram_name().c_str(),
@@ -471,7 +468,7 @@ void Histogram::WriteAsciiBucketContext(const int64 past,
                                         const Count current,
                                         const int64 remaining,
                                         const size_t i,
-                                        string* output) const {
+                                        std::string* output) const {
   double scaled_sum = (past + current + remaining) / 100.0;
   WriteAsciiBucketValue(current, scaled_sum, output);
   if (0 < i) {
@@ -515,7 +512,7 @@ void Histogram::GetCountAndBucketData(Count* count,
 
 LinearHistogram::~LinearHistogram() {}
 
-HistogramBase* LinearHistogram::FactoryGet(const string& name,
+HistogramBase* LinearHistogram::FactoryGet(const std::string& name,
                                            Sample minimum,
                                            Sample maximum,
                                            size_t bucket_count,
@@ -524,7 +521,7 @@ HistogramBase* LinearHistogram::FactoryGet(const string& name,
       name, minimum, maximum, bucket_count, flags, NULL);
 }
 
-HistogramBase* LinearHistogram::FactoryTimeGet(const string& name,
+HistogramBase* LinearHistogram::FactoryTimeGet(const std::string& name,
                                                TimeDelta minimum,
                                                TimeDelta maximum,
                                                size_t bucket_count,
@@ -587,7 +584,7 @@ HistogramType LinearHistogram::GetHistogramType() const {
   return LINEAR_HISTOGRAM;
 }
 
-LinearHistogram::LinearHistogram(const string& name,
+LinearHistogram::LinearHistogram(const std::string& name,
                                  Sample minimum,
                                  Sample maximum,
                                  const BucketRanges* ranges)
@@ -602,7 +599,7 @@ double LinearHistogram::GetBucketSize(Count current, size_t i) const {
   return current/denominator;
 }
 
-const string LinearHistogram::GetAsciiBucketRange(size_t i) const {
+const std::string LinearHistogram::GetAsciiBucketRange(size_t i) const {
   int range = ranges(i);
   BucketDescriptionMap::const_iterator it = bucket_description_.find(range);
   if (it == bucket_description_.end())
@@ -632,7 +629,7 @@ void LinearHistogram::InitializeBucketRanges(Sample minimum,
 
 // static
 HistogramBase* LinearHistogram::DeserializeInfoImpl(PickleIterator* iter) {
-  string histogram_name;
+  std::string histogram_name;
   int flags;
   int declared_min;
   int declared_max;
@@ -657,7 +654,8 @@ HistogramBase* LinearHistogram::DeserializeInfoImpl(PickleIterator* iter) {
 // This section provides implementation for BooleanHistogram.
 //------------------------------------------------------------------------------
 
-HistogramBase* BooleanHistogram::FactoryGet(const string& name, int32 flags) {
+HistogramBase* BooleanHistogram::FactoryGet(const std::string& name,
+                                            int32 flags) {
   HistogramBase* histogram = StatisticsRecorder::FindHistogram(name);
   if (!histogram) {
     // To avoid racy destruction at shutdown, the following will be leaked.
@@ -682,12 +680,12 @@ HistogramType BooleanHistogram::GetHistogramType() const {
   return BOOLEAN_HISTOGRAM;
 }
 
-BooleanHistogram::BooleanHistogram(const string& name,
+BooleanHistogram::BooleanHistogram(const std::string& name,
                                    const BucketRanges* ranges)
     : LinearHistogram(name, 1, 2, ranges) {}
 
 HistogramBase* BooleanHistogram::DeserializeInfoImpl(PickleIterator* iter) {
-  string histogram_name;
+  std::string histogram_name;
   int flags;
   int declared_min;
   int declared_max;
@@ -712,9 +710,10 @@ HistogramBase* BooleanHistogram::DeserializeInfoImpl(PickleIterator* iter) {
 // CustomHistogram:
 //------------------------------------------------------------------------------
 
-HistogramBase* CustomHistogram::FactoryGet(const string& name,
-                                           const vector<Sample>& custom_ranges,
-                                           int32 flags) {
+HistogramBase* CustomHistogram::FactoryGet(
+    const std::string& name,
+    const std::vector<Sample>& custom_ranges,
+    int32 flags) {
   CHECK(ValidateCustomRanges(custom_ranges));
 
   HistogramBase* histogram = StatisticsRecorder::FindHistogram(name);
@@ -742,9 +741,9 @@ HistogramType CustomHistogram::GetHistogramType() const {
 }
 
 // static
-vector<Sample> CustomHistogram::ArrayToCustomRanges(
+std::vector<Sample> CustomHistogram::ArrayToCustomRanges(
     const Sample* values, size_t num_values) {
-  vector<Sample> all_values;
+  std::vector<Sample> all_values;
   for (size_t i = 0; i < num_values; ++i) {
     Sample value = values[i];
     all_values.push_back(value);
@@ -756,7 +755,7 @@ vector<Sample> CustomHistogram::ArrayToCustomRanges(
   return all_values;
 }
 
-CustomHistogram::CustomHistogram(const string& name,
+CustomHistogram::CustomHistogram(const std::string& name,
                                  const BucketRanges* ranges)
     : Histogram(name,
                 ranges->range(1),
@@ -782,7 +781,7 @@ double CustomHistogram::GetBucketSize(Count current, size_t i) const {
 
 // static
 HistogramBase* CustomHistogram::DeserializeInfoImpl(PickleIterator* iter) {
-  string histogram_name;
+  std::string histogram_name;
   int flags;
   int declared_min;
   int declared_max;
@@ -795,7 +794,7 @@ HistogramBase* CustomHistogram::DeserializeInfoImpl(PickleIterator* iter) {
   }
 
   // First and last ranges are not serialized.
-  vector<Sample> sample_ranges(bucket_count - 1);
+  std::vector<Sample> sample_ranges(bucket_count - 1);
 
   for (size_t i = 0; i < sample_ranges.size(); ++i) {
     if (!iter->ReadInt(&sample_ranges[i]))
@@ -813,7 +812,7 @@ HistogramBase* CustomHistogram::DeserializeInfoImpl(PickleIterator* iter) {
 
 // static
 bool CustomHistogram::ValidateCustomRanges(
-    const vector<Sample>& custom_ranges) {
+    const std::vector<Sample>& custom_ranges) {
   bool has_valid_range = false;
   for (size_t i = 0; i < custom_ranges.size(); i++) {
     Sample sample = custom_ranges[i];
@@ -827,9 +826,9 @@ bool CustomHistogram::ValidateCustomRanges(
 
 // static
 BucketRanges* CustomHistogram::CreateBucketRangesFromCustomRanges(
-      const vector<Sample>& custom_ranges) {
+      const std::vector<Sample>& custom_ranges) {
   // Remove the duplicates in the custom ranges array.
-  vector<int> ranges = custom_ranges;
+  std::vector<int> ranges = custom_ranges;
   ranges.push_back(0);  // Ensure we have a zero value.
   ranges.push_back(HistogramBase::kSampleType_MAX);
   std::sort(ranges.begin(), ranges.end());
diff --git a/base/metrics/histogram_snapshot_manager.cc b/base/metrics/histogram_snapshot_manager.cc
index b1e26da..a7605aa 100644
--- a/base/metrics/histogram_snapshot_manager.cc
+++ b/base/metrics/histogram_snapshot_manager.cc
@@ -10,9 +10,6 @@
 #include "base/metrics/statistics_recorder.h"
 #include "base/stl_util.h"
 
-using std::map;
-using std::string;
-
 namespace base {
 
 HistogramSnapshotManager::HistogramSnapshotManager(
@@ -78,7 +75,7 @@ void HistogramSnapshotManager::PrepareDelta(const HistogramBase& histogram) {
   }
 
   HistogramSamples* to_log;
-  map<string, HistogramSamples*>::iterator it =
+  std::map<std::string, HistogramSamples*>::iterator it =
       logged_samples_.find(histogram_name);
   if (it == logged_samples_.end()) {
     to_log = snapshot.release();
diff --git a/base/metrics/histogram_unittest.cc b/base/metrics/histogram_unittest.cc
index df43e65..2e3a1ee 100644
--- a/base/metrics/histogram_unittest.cc
+++ b/base/metrics/histogram_unittest.cc
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Test of Histogram class
+#include "base/metrics/histogram.h"
 
 #include <climits>
 #include <algorithm>
@@ -11,15 +11,12 @@
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/metrics/bucket_ranges.h"
-#include "base/metrics/histogram.h"
 #include "base/metrics/sample_vector.h"
 #include "base/metrics/statistics_recorder.h"
 #include "base/pickle.h"
 #include "base/time/time.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
-using std::vector;
-
 namespace base {
 
 class HistogramTest : public testing::Test {
@@ -55,7 +52,7 @@ TEST_F(HistogramTest, BasicTest) {
       "TestLinearHistogram", 1, 1000, 10, HistogramBase::kNoFlags);
   EXPECT_TRUE(linear_histogram);
 
-  vector<int> custom_ranges;
+  std::vector<int> custom_ranges;
   custom_ranges.push_back(1);
   custom_ranges.push_back(5);
   HistogramBase* custom_histogram = CustomHistogram::FactoryGet(
@@ -157,7 +154,7 @@ TEST_F(HistogramTest, LinearRangesTest) {
 
 TEST_F(HistogramTest, ArrayToCustomRangesTest) {
   const HistogramBase::Sample ranges[3] = {5, 10, 20};
-  vector<HistogramBase::Sample> ranges_vec =
+  std::vector<HistogramBase::Sample> ranges_vec =
       CustomHistogram::ArrayToCustomRanges(ranges, 3);
   ASSERT_EQ(6u, ranges_vec.size());
   EXPECT_EQ(5, ranges_vec[0]);
@@ -170,7 +167,7 @@ TEST_F(HistogramTest, ArrayToCustomRangesTest) {
 
 TEST_F(HistogramTest, CustomHistogramTest) {
   // A well prepared custom ranges.
-  vector<HistogramBase::Sample> custom_ranges;
+  std::vector<HistogramBase::Sample> custom_ranges;
   custom_ranges.push_back(1);
   custom_ranges.push_back(2);
 
@@ -220,7 +217,7 @@ TEST_F(HistogramTest, CustomHistogramWithOnly2Buckets) {
   // We should probably change the restriction on the base class (or not inherit
   // the base class!).
 
-  vector<HistogramBase::Sample> custom_ranges;
+  std::vector<HistogramBase::Sample> custom_ranges;
   custom_ranges.push_back(4);
 
   Histogram* histogram = static_cast<Histogram*>(
@@ -256,7 +253,7 @@ TEST_F(HistogramTest, BoundsTest) {
   EXPECT_EQ(0, samples->GetCountAtIndex(array_size - 2));
   EXPECT_EQ(2, samples->GetCountAtIndex(array_size - 1));
 
-  vector<int> custom_ranges;
+  std::vector<int> custom_ranges;
   custom_ranges.push_back(10);
   custom_ranges.push_back(50);
   custom_ranges.push_back(100);
@@ -405,7 +402,7 @@ TEST_F(HistogramTest, HistogramSerializeInfo) {
 }
 
 TEST_F(HistogramTest, CustomHistogramSerializeInfo) {
-  vector<int> custom_ranges;
+  std::vector<int> custom_ranges;
   custom_ranges.push_back(10);
   custom_ranges.push_back(100);
 
@@ -484,7 +481,7 @@ TEST(HistogramDeathTest, BadRangesTest) {
       linear_histogram->HasConstructionArguments(
           1, HistogramBase::kSampleType_MAX - 1, 8));
 
-  vector<int> custom_ranges;
+  std::vector<int> custom_ranges;
   custom_ranges.push_back(0);
   custom_ranges.push_back(5);
   Histogram* custom_histogram = static_cast<Histogram*>(
diff --git a/base/metrics/sample_map.cc b/base/metrics/sample_map.cc
index 42468cb..00ac939 100644
--- a/base/metrics/sample_map.cc
+++ b/base/metrics/sample_map.cc
@@ -6,8 +6,6 @@
 
 #include "base/logging.h"
 
-using std::map;
-
 namespace base {
 
 typedef HistogramBase::Count Count;
@@ -24,7 +22,7 @@ void SampleMap::Accumulate(Sample value, Count count) {
 }
 
 Count SampleMap::GetCount(Sample value) const {
-  map<Sample, Count>::const_iterator it = sample_counts_.find(value);
+  std::map<Sample, Count>::const_iterator it = sample_counts_.find(value);
   if (it == sample_counts_.end())
     return 0;
   return it->second;
@@ -32,10 +30,8 @@ Count SampleMap::GetCount(Sample value) const {
 
 Count SampleMap::TotalCount() const {
   Count count = 0;
-  for (map<Sample, Count>::const_iterator it = sample_counts_.begin();
-       it != sample_counts_.end();
-       ++it) {
-    count += it->second;
+  for (const auto& entry : sample_counts_) {
+    count += entry.second;
   }
   return count;
 }
@@ -53,7 +49,8 @@ bool SampleMap::AddSubtractImpl(SampleCountIterator* iter,
     iter->Get(&min, &max, &count);
     if (min + 1 != max)
       return false;  // SparseHistogram only supports bucket with size 1.
-    sample_counts_[min] += (op ==  HistogramSamples::ADD) ? count : -count;
+
+    sample_counts_[min] += (op == HistogramSamples::ADD) ? count : -count;
   }
   return true;
 }
diff --git a/base/metrics/sample_map_unittest.cc b/base/metrics/sample_map_unittest.cc
index 1a53ee7..772c3da 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 {
diff --git a/base/metrics/sample_vector.cc b/base/metrics/sample_vector.cc
index ca3205e..1202527 100644
--- a/base/metrics/sample_vector.cc
+++ b/base/metrics/sample_vector.cc
@@ -7,8 +7,6 @@
 #include "base/logging.h"
 #include "base/metrics/bucket_ranges.h"
 
-using std::vector;
-
 namespace base {
 
 typedef HistogramBase::Count Count;
@@ -111,7 +109,7 @@ size_t SampleVector::GetBucketIndex(Sample value) const {
   return mid;
 }
 
-SampleVectorIterator::SampleVectorIterator(const vector<Count>* counts,
+SampleVectorIterator::SampleVectorIterator(const std::vector<Count>* counts,
                                            const BucketRanges* bucket_ranges)
     : counts_(counts),
       bucket_ranges_(bucket_ranges),
diff --git a/base/metrics/sample_vector_unittest.cc b/base/metrics/sample_vector_unittest.cc
index 9c7ba96..fd42376 100644
--- a/base/metrics/sample_vector_unittest.cc
+++ b/base/metrics/sample_vector_unittest.cc
@@ -2,16 +2,15 @@
 // 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 <vector>
 
 #include "base/memory/scoped_ptr.h"
 #include "base/metrics/bucket_ranges.h"
 #include "base/metrics/histogram.h"
-#include "base/metrics/sample_vector.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
-using std::vector;
-
 namespace base {
 namespace {
 
@@ -179,7 +178,7 @@ TEST(SampleVectorIteratorTest, IterateTest) {
   ranges.set_range(3, 3);
   ranges.set_range(4, 4);
 
-  vector<HistogramBase::Count> counts(3);
+  std::vector<HistogramBase::Count> counts(3);
   counts[0] = 1;
   counts[1] = 0;  // Iterator will bypass this empty bucket.
   counts[2] = 2;
diff --git a/base/metrics/sparse_histogram.cc b/base/metrics/sparse_histogram.cc
index 773eeb6..e5cdb43 100644
--- a/base/metrics/sparse_histogram.cc
+++ b/base/metrics/sparse_histogram.cc
@@ -10,16 +10,14 @@
 #include "base/strings/stringprintf.h"
 #include "base/synchronization/lock.h"
 
-using std::map;
-using std::string;
-
 namespace base {
 
 typedef HistogramBase::Count Count;
 typedef HistogramBase::Sample Sample;
 
 // static
-HistogramBase* SparseHistogram::FactoryGet(const string& name, int32 flags) {
+HistogramBase* SparseHistogram::FactoryGet(const std::string& name,
+                                           int32 flags) {
   HistogramBase* histogram = StatisticsRecorder::FindHistogram(name);
 
   if (!histogram) {
@@ -70,13 +68,13 @@ bool SparseHistogram::AddSamplesFromPickle(PickleIterator* iter) {
   return samples_.AddFromPickle(iter);
 }
 
-void SparseHistogram::WriteHTMLGraph(string* output) const {
+void SparseHistogram::WriteHTMLGraph(std::string* output) const {
   output->append("<PRE>");
   WriteAsciiImpl(true, "<br>", output);
   output->append("</PRE>");
 }
 
-void SparseHistogram::WriteAscii(string* output) const {
+void SparseHistogram::WriteAscii(std::string* output) const {
   WriteAsciiImpl(true, "\n", output);
 }
 
@@ -84,11 +82,11 @@ bool SparseHistogram::SerializeInfoImpl(Pickle* pickle) const {
   return pickle->WriteString(histogram_name()) && pickle->WriteInt(flags());
 }
 
-SparseHistogram::SparseHistogram(const string& name)
+SparseHistogram::SparseHistogram(const std::string& name)
     : HistogramBase(name) {}
 
 HistogramBase* SparseHistogram::DeserializeInfoImpl(PickleIterator* iter) {
-  string histogram_name;
+  std::string histogram_name;
   int flags;
   if (!iter->ReadString(&histogram_name) || !iter->ReadInt(&flags)) {
     DLOG(ERROR) << "Pickle error decoding Histogram: " << histogram_name;
@@ -129,8 +127,7 @@ void SparseHistogram::WriteAsciiImpl(bool graph_it,
   Count largest_count = 0;
   Sample largest_sample = 0;
   scoped_ptr<SampleCountIterator> it = snapshot->Iterator();
-  while (!it->Done())
-  {
+  while (!it->Done()) {
     Sample min;
     Sample max;
     Count count;
@@ -145,15 +142,14 @@ void SparseHistogram::WriteAsciiImpl(bool graph_it,
 
   // iterate over each item and display them
   it = snapshot->Iterator();
-  while (!it->Done())
-  {
+  while (!it->Done()) {
     Sample min;
     Sample max;
     Count count;
     it->Get(&min, &max, &count);
 
     // value is min, so display it
-    string range = GetSimpleAsciiBucketRange(min);
+    std::string range = GetSimpleAsciiBucketRange(min);
     output->append(range);
     for (size_t j = 0; range.size() + j < print_width + 1; ++j)
       output->push_back(' ');
diff --git a/base/metrics/sparse_histogram_unittest.cc b/base/metrics/sparse_histogram_unittest.cc
index c29dd5e..fca4d59 100644
--- a/base/metrics/sparse_histogram_unittest.cc
+++ b/base/metrics/sparse_histogram_unittest.cc
@@ -2,13 +2,14 @@
 // 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 <string>
 
 #include "base/memory/scoped_ptr.h"
 #include "base/metrics/histogram_base.h"
 #include "base/metrics/histogram_samples.h"
 #include "base/metrics/sample_map.h"
-#include "base/metrics/sparse_histogram.h"
 #include "base/metrics/statistics_recorder.h"
 #include "base/pickle.h"
 #include "base/strings/stringprintf.h"
diff --git a/base/metrics/statistics_recorder.cc b/base/metrics/statistics_recorder.cc
index fb069a5..85408e1 100644
--- a/base/metrics/statistics_recorder.cc
+++ b/base/metrics/statistics_recorder.cc
@@ -14,9 +14,6 @@
 #include "base/synchronization/lock.h"
 #include "base/values.h"
 
-using std::list;
-using std::string;
-
 namespace {
 // Initialize histogram statistics gathering system.
 base::LazyInstance<base::StatisticsRecorder>::Leaky g_statistics_recorder_ =
@@ -59,7 +56,7 @@ HistogramBase* StatisticsRecorder::RegisterOrDeleteDuplicate(
     if (histograms_ == NULL) {
       histogram_to_return = histogram;
     } else {
-      const string& name = histogram->histogram_name();
+      const std::string& name = histogram->histogram_name();
       HistogramMap::iterator it = histograms_->find(name);
       if (histograms_->end() == it) {
         (*histograms_)[name] = histogram;
@@ -96,22 +93,18 @@ const BucketRanges* StatisticsRecorder::RegisterOrDeleteDuplicateRanges(
     return ranges;
   }
 
-  list<const BucketRanges*>* checksum_matching_list;
+  std::list<const BucketRanges*>* checksum_matching_list;
   RangesMap::iterator ranges_it = ranges_->find(ranges->checksum());
   if (ranges_->end() == ranges_it) {
     // Add a new matching list to map.
-    checksum_matching_list = new list<const BucketRanges*>();
+    checksum_matching_list = new std::list<const BucketRanges*>();
     ANNOTATE_LEAKING_OBJECT_PTR(checksum_matching_list);
     (*ranges_)[ranges->checksum()] = checksum_matching_list;
   } else {
     checksum_matching_list = ranges_it->second;
   }
 
-  list<const BucketRanges*>::iterator checksum_matching_list_it;
-  for (checksum_matching_list_it = checksum_matching_list->begin();
-       checksum_matching_list_it != checksum_matching_list->end();
-       ++checksum_matching_list_it) {
-    const BucketRanges* existing_ranges = *checksum_matching_list_it;
+  for (const BucketRanges* existing_ranges : *checksum_matching_list) {
     if (existing_ranges->Equals(ranges)) {
       if (existing_ranges == ranges) {
         return ranges;
@@ -135,10 +128,8 @@ void StatisticsRecorder::WriteHTMLGraph(const std::string& query,
 
   Histograms snapshot;
   GetSnapshot(query, &snapshot);
-  for (Histograms::iterator it = snapshot.begin();
-       it != snapshot.end();
-       ++it) {
-    (*it)->WriteHTMLGraph(output);
+  for (const HistogramBase* histogram : snapshot) {
+    histogram->WriteHTMLGraph(output);
     output->append("<br><hr><br>");
   }
 }
@@ -155,10 +146,8 @@ void StatisticsRecorder::WriteGraph(const std::string& query,
 
   Histograms snapshot;
   GetSnapshot(query, &snapshot);
-  for (Histograms::iterator it = snapshot.begin();
-       it != snapshot.end();
-       ++it) {
-    (*it)->WriteAscii(output);
+  for (const HistogramBase* histogram : snapshot) {
+    histogram->WriteAscii(output);
     output->append("\n");
   }
 }
@@ -179,14 +168,13 @@ std::string StatisticsRecorder::ToJSON(const std::string& query) {
   GetSnapshot(query, &snapshot);
   output += "\"histograms\":[";
   bool first_histogram = true;
-  for (Histograms::const_iterator it = snapshot.begin(); it != snapshot.end();
-       ++it) {
+  for (const HistogramBase* histogram : snapshot) {
     if (first_histogram)
       first_histogram = false;
     else
       output += ",";
     std::string json;
-    (*it)->WriteJSON(&json);
+    histogram->WriteJSON(&json);
     output += json;
   }
   output += "]}";
@@ -201,11 +189,9 @@ void StatisticsRecorder::GetHistograms(Histograms* output) {
   if (histograms_ == NULL)
     return;
 
-  for (HistogramMap::iterator it = histograms_->begin();
-       histograms_->end() != it;
-       ++it) {
-    DCHECK_EQ(it->first, it->second->histogram_name());
-    output->push_back(it->second);
+  for (const auto& entry : *histograms_) {
+    DCHECK_EQ(entry.first, entry.second->histogram_name());
+    output->push_back(entry.second);
   }
 }
 
@@ -218,15 +204,9 @@ void StatisticsRecorder::GetBucketRanges(
   if (ranges_ == NULL)
     return;
 
-  for (RangesMap::iterator it = ranges_->begin();
-       ranges_->end() != it;
-       ++it) {
-    list<const BucketRanges*>* ranges_list = it->second;
-    list<const BucketRanges*>::iterator ranges_list_it;
-    for (ranges_list_it = ranges_list->begin();
-         ranges_list_it != ranges_list->end();
-         ++ranges_list_it) {
-      output->push_back(*ranges_list_it);
+  for (const auto& entry : *ranges_) {
+    for (const auto& range_entry : *entry.second) {
+      output->push_back(range_entry);
     }
   }
 }
@@ -254,11 +234,9 @@ void StatisticsRecorder::GetSnapshot(const std::string& query,
   if (histograms_ == NULL)
     return;
 
-  for (HistogramMap::iterator it = histograms_->begin();
-       histograms_->end() != it;
-       ++it) {
-    if (it->first.find(query) != std::string::npos)
-      snapshot->push_back(it->second);
+  for (const auto& entry : *histograms_) {
+    if (entry.first.find(query) != std::string::npos)
+      snapshot->push_back(entry.second);
   }
 }
 
@@ -286,7 +264,7 @@ StatisticsRecorder::StatisticsRecorder() {
 
 // static
 void StatisticsRecorder::DumpHistogramsToVlog(void* instance) {
-  string output;
+  std::string output;
   StatisticsRecorder::WriteGraph(std::string(), &output);
   VLOG(1) << output;
 }