Add ownership-transfer to histogram management calls.

base/metrics/statistics_recorder.cc

Index: base/metrics/statistics_recorder.cc
diff --git a/base/metrics/statistics_recorder.cc b/base/metrics/statistics_recorder.cc
index d0fa2add3603b3f574dfa9ef9e5ee2e6b152aafc..3d8504baa1ef5ddf68585080652c5a6adf1fb19e 100644
--- a/base/metrics/statistics_recorder.cc
+++ b/base/metrics/statistics_recorder.cc
@@ -83,7 +83,11 @@ bool StatisticsRecorder::IsActive() {
 
 // static
 HistogramBase* StatisticsRecorder::RegisterOrDeleteDuplicate(
-    HistogramBase* histogram) {
+    scoped_ptr<HistogramBase> histogram_ptr) {
+  // Ownership is managed outside of scoped_ptr, the use of which is only to
+  // explicitly document the transfer of ownership during the call.
+  HistogramBase* histogram = histogram_ptr.release();
+
   // As per crbug.com/79322 the histograms are intentionally leaked, so we need
   // to annotate them. Because ANNOTATE_LEAKING_OBJECT_PTR may be used only once
   // for an object, the duplicates should not be annotated.
@@ -119,7 +123,9 @@ HistogramBase* StatisticsRecorder::RegisterOrDeleteDuplicate(
         }
         histogram_to_return = histogram;
       } else if (histogram == it->second) {
-        // The histogram was registered before.
+        // The histogram was registered before. This should never happen since
+        // the method signature ensures moving of the histogram pointer.
+        NOTREACHED();
         histogram_to_return = histogram;
       } else {
         // We already have one histogram with this name.
@@ -136,7 +142,11 @@ HistogramBase* StatisticsRecorder::RegisterOrDeleteDuplicate(
 
 // static
 const BucketRanges* StatisticsRecorder::RegisterOrDeleteDuplicateRanges(
-    const BucketRanges* ranges) {
+    scoped_ptr<const BucketRanges> ranges_ptr) {
+  // Ownership is managed outside of scoped_ptr, the use of which is only to
+  // explicitly document the transfer of ownership during the call.
+  const BucketRanges* ranges = ranges_ptr.release();
+
   DCHECK(ranges->HasValidChecksum());
   scoped_ptr<const BucketRanges> ranges_deleter;