Convert //ash from scoped_ptr to std::unique_ptr

ash/system/tray/system_tray_bubble.h

Index: ash/system/tray/system_tray_bubble.h
diff --git a/ash/system/tray/system_tray_bubble.h b/ash/system/tray/system_tray_bubble.h
index 4dd9bc4ca7d807d4c41e2cb119943ee46c6a9869..1d098a31240c7545b431b50d449f938310b6c557 100644
--- a/ash/system/tray/system_tray_bubble.h
+++ b/ash/system/tray/system_tray_bubble.h
@@ -5,14 +5,14 @@
 #ifndef ASH_SYSTEM_TRAY_SYSTEM_TRAY_BUBBLE_H_
 #define ASH_SYSTEM_TRAY_SYSTEM_TRAY_BUBBLE_H_
 
+#include <memory>
+#include <vector>
+
 #include "ash/system/user/login_status.h"
 #include "base/macros.h"
-#include "base/memory/scoped_ptr.h"
 #include "base/timer/timer.h"
 #include "ui/views/bubble/tray_bubble_view.h"
 
-#include <vector>
-
 namespace ash {
 class SystemTray;
 class SystemTrayItem;