Add ownership-transfer to histogram management calls.

base/metrics/statistics_recorder.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/metrics/statistics_recorder.h"
 
 #include "base/at_exit.h"
 #include "base/debug/leak_annotations.h"
 #include "base/json/string_escape.h"
 #include "base/logging.h"
@@ skipping 65 matching lines @@
 // static
 bool StatisticsRecorder::IsActive() {
   if (lock_ == NULL)
     return false;
   base::AutoLock auto_lock(*lock_);
   return NULL != histograms_;
 }
 
 // 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.
   // Callers are responsible for not calling RegisterOrDeleteDuplicate(ptr)
   // twice if (lock_ == NULL) || (!histograms_).
   if (lock_ == NULL) {
     ANNOTATE_LEAKING_OBJECT_PTR(histogram);  // see crbug.com/79322
     return histogram;
   }
 
@@ skipping 15 matching lines @@
         // flag.
         auto callback_iterator = callbacks_->find(name);
         if (callback_iterator != callbacks_->end()) {
           if (!callback_iterator->second.is_null())
             histogram->SetFlags(HistogramBase::kCallbackExists);
           else
             histogram->ClearFlags(HistogramBase::kCallbackExists);
         }
         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.
         DCHECK_EQ(histogram->histogram_name(),
                   it->second->histogram_name()) << "hash collision";
         histogram_to_return = it->second;
         histogram_to_delete = histogram;
       }
     }
   }
   delete histogram_to_delete;
   return histogram_to_return;
 }
 
 // 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;
 
   if (lock_ == NULL) {
     ANNOTATE_LEAKING_OBJECT_PTR(ranges);
     return ranges;
   }
 
   base::AutoLock auto_lock(*lock_);
   if (ranges_ == NULL) {
@@ skipping 294 matching lines @@
 // static
 StatisticsRecorder::HistogramMap* StatisticsRecorder::histograms_ = NULL;
 // static
 StatisticsRecorder::CallbackMap* StatisticsRecorder::callbacks_ = NULL;
 // static
 StatisticsRecorder::RangesMap* StatisticsRecorder::ranges_ = NULL;
 // static
 base::Lock* StatisticsRecorder::lock_ = NULL;
 
 }  // namespace base