first pass histogram shrink

base/metrics/histogram.cc

Index: base/metrics/histogram.cc
diff --git a/base/metrics/histogram.cc b/base/metrics/histogram.cc
index fbe66d05d29fd3c2896f8499dd1dc07d9793d095..579bac48e2e6f9491c08119c01665e9bdcdddb49 100644
--- a/base/metrics/histogram.cc
+++ b/base/metrics/histogram.cc
@@ -123,6 +123,20 @@ HistogramBase* Histogram::FactoryTimeGet(const string& name,
                     bucket_count, flags);
 }
 
+HistogramBase* Histogram::FactoryTimeGetAndAtomicRelease(
+    base::subtle::AtomicWord* atomic_histogram_pointer,
+    const string& name,
+                                         TimeDelta minimum,
+                                         TimeDelta maximum,
+                                         size_t bucket_count,
+                                         int32 flags) {
+  HistogramBase* retval = FactoryGet(name, minimum.InMilliseconds(), maximum.InMilliseconds(),
+                                     bucket_count, flags);
+  base::subtle::Release_Store(atomic_histogram_pointer,
+                              reinterpret_cast<base::subtle::AtomicWord>(retval));
+  return retval;
+}
+
 TimeTicks Histogram::DebugNow() {
 #ifndef NDEBUG
   return TimeTicks::Now();