Update from https://crrev.com/333737

base/metrics/sparse_histogram.cc

Index: base/metrics/sparse_histogram.cc
diff --git a/base/metrics/sparse_histogram.cc b/base/metrics/sparse_histogram.cc
index 773eeb6273c5f8feef7eb77b545cf978d882a223..e5cdb43c04fea1514a032ca3e5c311899a979af4 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(' ');