Add ownership-transfer to histogram management calls.

base/metrics/histogram_persistence.cc

Index: base/metrics/histogram_persistence.cc
diff --git a/base/metrics/histogram_persistence.cc b/base/metrics/histogram_persistence.cc
index bd250ec888a62a1998a4e762576b6bac388408b2..16b76d8fca3a5c403838e69ece65ffc22186e39c 100644
--- a/base/metrics/histogram_persistence.cc
+++ b/base/metrics/histogram_persistence.cc
@@ -228,7 +228,7 @@ ReleasePersistentHistogramMemoryAllocatorForTesting() {
   return allocator;
 };
 
-HistogramBase* CreatePersistentHistogram(
+scoped_ptr<HistogramBase> CreatePersistentHistogram(
     PersistentMemoryAllocator* allocator,
     PersistentHistogramData* histogram_data_ptr) {
   if (!histogram_data_ptr) {
@@ -257,17 +257,19 @@ HistogramBase* CreatePersistentHistogram(
     NOTREACHED();
     return nullptr;
   }
-  // To avoid racy destruction at shutdown, the following will be leaked.
-  const BucketRanges* ranges = CreateRangesFromData(
+
+  scoped_ptr<const BucketRanges> created_ranges(CreateRangesFromData(
       ranges_data,
       histogram_data.ranges_checksum,
-      histogram_data.bucket_count + 1);
-  if (!ranges) {
+      histogram_data.bucket_count + 1));
+  if (!created_ranges) {
     RecordCreateHistogramResult(CREATE_HISTOGRAM_INVALID_RANGES_ARRAY);
     NOTREACHED();
     return nullptr;
   }
-  ranges = StatisticsRecorder::RegisterOrDeleteDuplicateRanges(ranges);
+  const BucketRanges* ranges =
+      StatisticsRecorder::RegisterOrDeleteDuplicateRanges(
+          std::move(created_ranges));
 
   HistogramBase::AtomicCount* counts_data =
       allocator->GetAsObject<HistogramBase::AtomicCount>(
@@ -288,10 +290,10 @@ HistogramBase* CreatePersistentHistogram(
       counts_data + histogram_data.bucket_count;
 
   std::string name(histogram_data_ptr->name);
-  HistogramBase* histogram = nullptr;
+  scoped_ptr<HistogramBase> histogram;
   switch (histogram_data.histogram_type) {
     case HISTOGRAM:
-      histogram = Histogram::PersistentGet(
+      histogram.reset(Histogram::PersistentGet(
           name,
           histogram_data.minimum,
           histogram_data.maximum,
@@ -300,11 +302,11 @@ HistogramBase* CreatePersistentHistogram(
           logged_data,
           histogram_data.bucket_count,
           &histogram_data_ptr->samples_metadata,
-          &histogram_data_ptr->logged_metadata);
+          &histogram_data_ptr->logged_metadata));
       DCHECK(histogram);
       break;
     case LINEAR_HISTOGRAM:
-      histogram = LinearHistogram::PersistentGet(
+      histogram.reset(LinearHistogram::PersistentGet(
           name,
           histogram_data.minimum,
           histogram_data.maximum,
@@ -313,28 +315,28 @@ HistogramBase* CreatePersistentHistogram(
           logged_data,
           histogram_data.bucket_count,
           &histogram_data_ptr->samples_metadata,
-          &histogram_data_ptr->logged_metadata);
+          &histogram_data_ptr->logged_metadata));
       DCHECK(histogram);
       break;
     case BOOLEAN_HISTOGRAM:
-      histogram = BooleanHistogram::PersistentGet(
+      histogram.reset(BooleanHistogram::PersistentGet(
           name,
           ranges,
           counts_data,
           logged_data,
           &histogram_data_ptr->samples_metadata,
-          &histogram_data_ptr->logged_metadata);
+          &histogram_data_ptr->logged_metadata));
       DCHECK(histogram);
       break;
     case CUSTOM_HISTOGRAM:
-      histogram = CustomHistogram::PersistentGet(
+      histogram.reset(CustomHistogram::PersistentGet(
           name,
           ranges,
           counts_data,
           logged_data,
           histogram_data.bucket_count,
           &histogram_data_ptr->samples_metadata,
-          &histogram_data_ptr->logged_metadata);
+          &histogram_data_ptr->logged_metadata));
       DCHECK(histogram);
       break;
     default:
@@ -352,7 +354,7 @@ HistogramBase* CreatePersistentHistogram(
   return histogram;
 }
 
-HistogramBase* GetPersistentHistogram(
+scoped_ptr<HistogramBase> GetPersistentHistogram(
     PersistentMemoryAllocator* allocator,
     int32_t ref) {
   // Unfortunately, the above "pickle" methods cannot be used as part of the
@@ -372,7 +374,7 @@ HistogramBase* GetPersistentHistogram(
   return CreatePersistentHistogram(allocator, histogram_data);
 }
 
-HistogramBase* GetNextPersistentHistogram(
+scoped_ptr<HistogramBase> GetNextPersistentHistogram(
     PersistentMemoryAllocator* allocator,
     PersistentMemoryAllocator::Iterator* iter) {
   PersistentMemoryAllocator::Reference ref;
@@ -397,7 +399,7 @@ void FinalizePersistentHistogram(PersistentMemoryAllocator::Reference ref,
     GetPersistentHistogramMemoryAllocator()->SetType(ref, 0);
 }
 
-HistogramBase* AllocatePersistentHistogram(
+scoped_ptr<HistogramBase> AllocatePersistentHistogram(
     PersistentMemoryAllocator* allocator,
     HistogramType histogram_type,
     const std::string& name,
@@ -465,8 +467,8 @@ HistogramBase* AllocatePersistentHistogram(
     // using what is already known above but avoids duplicating the switch
     // statement here and serves as a double-check that everything is
     // correct before commiting the new histogram to persistent space.
-    HistogramBase* histogram =
-        CreatePersistentHistogram(allocator, histogram_data);
+    scoped_ptr<HistogramBase> histogram(
+        CreatePersistentHistogram(allocator, histogram_data));
     DCHECK(histogram);
     if (ref_ptr != nullptr)
       *ref_ptr = histogram_ref;
@@ -504,10 +506,11 @@ void ImportPersistentHistograms() {
       g_allocator->CreateIterator(&iter);
 
     while (true) {
-      HistogramBase* histogram = GetNextPersistentHistogram(g_allocator, &iter);
+      scoped_ptr<HistogramBase> histogram(
+          GetNextPersistentHistogram(g_allocator, &iter));
       if (!histogram)
         break;
-      StatisticsRecorder::RegisterOrDeleteDuplicate(histogram);
+      StatisticsRecorder::RegisterOrDeleteDuplicate(std::move(histogram));
     }
   }
 }