Fix possible memory leak due to tooltip property in aura::Window

content/browser/renderer_host/render_widget_host_view_aura.h

 // Copyright (c) 2011 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 CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_AURA_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_AURA_H_
 #pragma once
 
 #include <map>
 
@@ skipping 125 matching lines @@
   bool is_loading_;
 
   // The cursor for the page. This is passed up from the renderer.
   WebCursor current_cursor_;
 
   // The touch-event. Its touch-points are updated as necessary. A new
   // touch-point is added from an ET_TOUCH_PRESSED event, and a touch-point is
   // removed from the list on an ET_TOUCH_RELEASED event.
   WebKit::WebTouchEvent touch_event_;
 
+  // Current tooltip text.
+  string16 tooltip_;
+
 #if defined(UI_COMPOSITOR_IMAGE_TRANSPORT)
   std::vector< base::Callback<void(void)> > on_compositing_ended_callbacks_;
 
   std::map<uint64, scoped_refptr<AcceleratedSurfaceContainerLinux> >
       accelerated_surface_containers_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostViewAura);
 };
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_AURA_H_