Fix memory leak in NotificationControlButtonsView

ui/message_center/views/notification_control_buttons_view.h

 // Copyright 2017 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/macros.h"
 #include "third_party/skia/include/core/SkColor.h"
 #include "ui/gfx/animation/animation_delegate.h"
 #include "ui/message_center/message_center_export.h"
 #include "ui/views/controls/button/button.h"
 #include "ui/views/view.h"
@@ skipping 33 matching lines @@
   // Request the focus on the close button.
   void RequestFocusOnCloseButton();
 
   // Return the focus status of the close button. True if the focus is on the
   // close button, false otherwise.
   bool IsCloseButtonFocused() const;
   // Return the focus status of the settings button. True if the focus is on the
   // close button, false otherwise.
   bool IsSettingsButtonFocused() const;
 
-  message_center::PaddedButton* close_button_for_testing() const {
-    return close_button_;
-  }
-  message_center::PaddedButton* settings_button_for_testing() const {
-    return settings_button_;
-  }
+  // Methods for testing.
+  message_center::PaddedButton* close_button_for_testing() const;
+  message_center::PaddedButton* settings_button_for_testing() const;
 
   // views::View
   const char* GetClassName() const override;
 
   // views::ButtonListener
   void ButtonPressed(views::Button* sender, const ui::Event& event) override;
 
   // gfx::AnimationDelegate
   void AnimationEnded(const gfx::Animation* animation) override;
   void AnimationProgressed(const gfx::Animation* animation) override;
   void AnimationCanceled(const gfx::Animation* animation) override;
 
  private:
   MessageView* message_view_;
 
-  message_center::PaddedButton* close_button_ = nullptr;
-  message_center::PaddedButton* settings_button_ = nullptr;
+  std::unique_ptr<message_center::PaddedButton> close_button_;
+  std::unique_ptr<message_center::PaddedButton> settings_button_;
 
   std::unique_ptr<gfx::LinearAnimation> bgcolor_animation_;
   SkColor bgcolor_origin_;
   SkColor bgcolor_target_;
 
   DISALLOW_COPY_AND_ASSIGN(NotificationControlButtonsView);
 };
 
 }  // namespace message_center