Aura: notify DropHelper when target view is removed.

ui/aura_shell/shadow.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 UI_AURA_SHELL_SHADOW_H_
 #define UI_AURA_SHELL_SHADOW_H_
 #pragma once
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
+#include "ui/aura_shell/aura_shell_export.h"
 #include "ui/gfx/rect.h"
 
 namespace ui {
 class Layer;
 }  // namespace ui
 
 namespace aura_shell {
 namespace internal {
 
 class ImageGrid;
 
 // Simple class that draws a drop shadow around content at given bounds.
-class Shadow {
+class AURA_SHELL_EXPORT Shadow {
  public:
   Shadow();
   ~Shadow();
 
   // Returns |image_grid_|'s ui::Layer.  This is exposed so it can be added to
   // the same layer as the content and stacked below it.  SetContentBounds()
   // should be used to adjust the shadow's size and position (rather than
   // applying transformations to this layer).
   ui::Layer* layer() const;
 
@@ skipping 10 matching lines @@
   // Bounds of the content that the shadow encloses.
   gfx::Rect content_bounds_;
 
   DISALLOW_COPY_AND_ASSIGN(Shadow);
 };
 
 }  // namespace internal
 }  // namespace aura_shell
 
 #endif  // UI_AURA_SHELL_SHADOW_H_