Add ownership-transfer to histogram management calls.

base/metrics/histogram.h

Index: base/metrics/histogram.h
diff --git a/base/metrics/histogram.h b/base/metrics/histogram.h
index ea59de64c249352aec0ef3876c753852e35b6d02..19b01466711cd8adf7a5dca6a082949dafca945b 100644
--- a/base/metrics/histogram.h
+++ b/base/metrics/histogram.h
@@ -104,6 +104,8 @@ class BASE_EXPORT Histogram : public HistogramBase {
 
   typedef std::vector<Count> Counts;
 
+  ~Histogram() override;
+
   //----------------------------------------------------------------------------
   // For a valid histogram, input should follow these restrictions:
   // minimum > 0 (if a minimum below 1 is specified, it will implicitly be
@@ -237,8 +239,6 @@ class BASE_EXPORT Histogram : public HistogramBase {
             HistogramSamples::Metadata* meta,
             HistogramSamples::Metadata* logged_meta);
 
-  ~Histogram() override;
-
   // HistogramBase implementation:
   bool SerializeInfoImpl(base::Pickle* pickle) const override;