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

ash/common/wm/overview/window_selector_item.h

Index: ash/common/wm/overview/window_selector_item.h
diff --git a/ash/common/wm/overview/window_selector_item.h b/ash/common/wm/overview/window_selector_item.h
index ec503d28ed937405d3331c2876907469c3c6aa8a..bf62659ca3f491090ec49e84d788cf4f0dc88139 100644
--- a/ash/common/wm/overview/window_selector_item.h
+++ b/ash/common/wm/overview/window_selector_item.h
@@ -21,6 +21,10 @@ namespace views {
 class ImageButton;
 }
 
+namespace wm {
+class Shadow;
+}
+
 namespace ash {
 
 class WindowSelector;
@@ -174,6 +178,9 @@ class ASH_EXPORT WindowSelectorItem : public views::ButtonListener,
   // Otherwise it is shown under the window.
   std::unique_ptr<views::Widget> window_label_;
 
+  // Shadow around the item in overview.
+  std::unique_ptr<::wm::Shadow> shadow_;
+
   // Label background widget used to fade in opacity when moving selection.
   std::unique_ptr<views::Widget> window_label_selector_;