base: Use std::move() instead of Pass() for real movable types.

base/metrics/histogram.cc

Index: base/metrics/histogram.cc
diff --git a/base/metrics/histogram.cc b/base/metrics/histogram.cc
index b37bc4c4685c5476c9145a81bb953ddfbc2532d5..1bbcab7023a8be9e45e3ca72fb631abee31ef4a6 100644
--- a/base/metrics/histogram.cc
+++ b/base/metrics/histogram.cc
@@ -293,7 +293,7 @@ void Histogram::AddCount(int value, int count) {
 }
 
 scoped_ptr<HistogramSamples> Histogram::SnapshotSamples() const {
-  return SnapshotSampleVector().Pass();
+  return SnapshotSampleVector();
 }
 
 void Histogram::AddSamples(const HistogramSamples& samples) {
@@ -394,7 +394,7 @@ HistogramBase* Histogram::DeserializeInfoImpl(PickleIterator* iter) {
 scoped_ptr<SampleVector> Histogram::SnapshotSampleVector() const {
   scoped_ptr<SampleVector> samples(new SampleVector(bucket_ranges()));
   samples->Add(*samples_);
-  return samples.Pass();
+  return samples;
 }
 
 void Histogram::WriteAsciiImpl(bool graph_it,