[ash-md] Implements a shadow over overview items and selector

ash/common/wm/overview/window_grid.h

 // Copyright 2014 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 ASH_COMMON_WM_OVERVIEW_WINDOW_GRID_H_
 #define ASH_COMMON_WM_OVERVIEW_WINDOW_GRID_H_
 
 #include <stddef.h>
 
 #include <memory>
 #include <set>
 #include <vector>
 
 #include "ash/common/wm/overview/window_selector.h"
 #include "ash/common/wm_window_observer.h"
 #include "base/macros.h"
 #include "base/memory/scoped_vector.h"
 
 namespace views {
 class Widget;
 }
 
+namespace wm {
+class Shadow;
+}
+
 namespace ash {
 
 class WindowSelectorItem;
 
 // Represents a grid of windows in the Overview Mode in a particular root
 // window, and manages a selection widget that can be moved with the arrow keys.
 // The idea behind the movement strategy is that it should be possible to access
 // any window pressing a given arrow key repeatedly.
 // +-------+  +-------+  +-------+
 // |   0   |  |   1   |  |   2   |
@@ skipping 134 matching lines @@
 
   // Vector containing the observed windows.
   std::set<WmWindow*> observed_windows_;
 
   // Widget that darkens the screen background.
   std::unique_ptr<views::Widget> shield_widget_;
 
   // Widget that indicates to the user which is the selected window.
   std::unique_ptr<views::Widget> selection_widget_;
 
+  // Shadow around the selector.
+  std::unique_ptr<::wm::Shadow> selector_shadow_;
+
   // Current selected window position.
   size_t selected_index_;
 
   // Number of columns in the grid.
   size_t num_columns_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowGrid);
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_WM_OVERVIEW_WINDOW_GRID_H_