Use std::unique_ptr to transfer base::Value ownership in extensions::ValueStoreChange

extensions/browser/value_store/value_store_change.h

 // Copyright 2014 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.
 
 #ifndef EXTENSIONS_BROWSER_VALUE_STORE_VALUE_STORE_CHANGE_H_
 #define EXTENSIONS_BROWSER_VALUE_STORE_VALUE_STORE_CHANGE_H_
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/memory/ref_counted.h"
 #include "base/values.h"
 
 class ValueStoreChange;
 typedef std::vector<ValueStoreChange> ValueStoreChangeList;
 
 // A change to a setting.  Safe/efficient to copy.
 class ValueStoreChange {
  public:
   // Converts an ValueStoreChangeList into JSON of the form:
   // { "foo": { "key": "foo", "oldValue": "bar", "newValue": "baz" } }
   static std::string ToJson(const ValueStoreChangeList& changes);
 
-  // Ownership of |old_value| and |new_value| taken.
-  ValueStoreChange(
-      const std::string& key, base::Value* old_value, base::Value* new_value);
+  ValueStoreChange(const std::string& key,
+                   std::unique_ptr<base::Value> old_value,
+                   std::unique_ptr<base::Value> new_value);
 
   ValueStoreChange(const ValueStoreChange& other);
 
   ~ValueStoreChange();
 
   // Gets the key of the setting which changed.
   const std::string& key() const;
 
   // Gets the value of the setting before the change, or NULL if there was no
   // old value.
   const base::Value* old_value() const;
 
   // Gets the value of the setting after the change, or NULL if there is no new
   // value.
   const base::Value* new_value() const;
 
  private:
   class Inner : public base::RefCountedThreadSafe<Inner> {
    public:
-    Inner(
-        const std::string& key, base::Value* old_value, base::Value* new_value);
+    Inner(const std::string& key,
+          std::unique_ptr<base::Value> old_value,
+          std::unique_ptr<base::Value> new_value);
 
     const std::string key_;
     const std::unique_ptr<base::Value> old_value_;
     const std::unique_ptr<base::Value> new_value_;
 
    private:
     friend class base::RefCountedThreadSafe<Inner>;
     virtual ~Inner();
   };
 
   scoped_refptr<Inner> inner_;
 };
 
 #endif  // EXTENSIONS_BROWSER_VALUE_STORE_VALUE_STORE_CHANGE_H_