ash::ShelfView: CHECK against potentially bad static_casts.

ash/shelf/shelf_button.h

Index: ash/shelf/shelf_button.h
diff --git a/ash/shelf/shelf_button.h b/ash/shelf/shelf_button.h
index 45d7174c40a54af71c78b8e3e7ece554a353903d..d72c630c5902294716bc5095ea05af747030e7a7 100644
--- a/ash/shelf/shelf_button.h
+++ b/ash/shelf/shelf_button.h
@@ -17,6 +17,8 @@ class ShelfLayoutManager;
 // Button used for items on the launcher, except for the AppList.
 class ASH_EXPORT ShelfButton : public views::CustomButton {
  public:
+  static const char kViewClassName[];
+
   // Used to indicate the current state of the button.
   enum State {
     // Nothing special. Usually represents an app shortcut item with no running
@@ -91,6 +93,7 @@ class ASH_EXPORT ShelfButton : public views::CustomButton {
   };
 
   // View overrides:
+  virtual const char* GetClassName() const OVERRIDE;
   virtual bool OnMousePressed(const ui::MouseEvent& event) OVERRIDE;
   virtual void OnMouseReleased(const ui::MouseEvent& event) OVERRIDE;
   virtual bool OnMouseDragged(const ui::MouseEvent& event) OVERRIDE;