Use lock-free lazy initialization for static histogram references

chrome/browser/chromeos/external_metrics.cc

Index: chrome/browser/chromeos/external_metrics.cc
===================================================================
--- chrome/browser/chromeos/external_metrics.cc	(revision 80220)
+++ chrome/browser/chromeos/external_metrics.cc	(working copy)
@@ -86,7 +86,7 @@
   }
   // Do not use the UMA_HISTOGRAM_... macros here.  They cache the Histogram
   // instance and thus only work if |name| is constant.
-  scoped_refptr<base::Histogram> counter = base::Histogram::FactoryGet(
+  base::Histogram* counter = base::Histogram::FactoryGet(
       name, min, max, nbuckets, base::Histogram::kUmaTargetedHistogramFlag);
   counter->Add(sample);
 }
@@ -101,7 +101,7 @@
   }
   // Do not use the UMA_HISTOGRAM_... macros here.  They cache the Histogram
   // instance and thus only work if |name| is constant.
-  scoped_refptr<base::Histogram> counter = base::LinearHistogram::FactoryGet(
+  base::Histogram* counter = base::LinearHistogram::FactoryGet(
       name, 1, max, max + 1, base::Histogram::kUmaTargetedHistogramFlag);
   counter->Add(sample);
 }