Update from https://crrev.com/333737

base/metrics/histogram_samples.h

 // 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.
 
 #ifndef BASE_METRICS_HISTOGRAM_SAMPLES_H_
 #define BASE_METRICS_HISTOGRAM_SAMPLES_H_
 
 #include "base/basictypes.h"
 #include "base/metrics/histogram_base.h"
 #include "base/memory/scoped_ptr.h"
 
+namespace base {
+
 class Pickle;
 class PickleIterator;
-
-namespace base {
-
 class SampleCountIterator;
 
 // HistogramSamples is a container storing all samples of a histogram.
 class BASE_EXPORT HistogramSamples {
  public:
   HistogramSamples();
   virtual ~HistogramSamples();
 
   virtual void Accumulate(HistogramBase::Sample value,
                           HistogramBase::Count count) = 0;
@@ skipping 53 matching lines @@
 
   // Get the index of current histogram bucket.
   // For histograms that don't use predefined buckets, it returns false.
   // Requires: !Done();
   virtual bool GetBucketIndex(size_t* index) const;
 };
 
 }  // namespace base
 
 #endif  // BASE_METRICS_HISTOGRAM_SAMPLES_H_