Gut ash::MaterialDesignController, and remove the about:flags entry.

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 ccd3959fa12160812e36e1b09c0df8e2589ca648..2d8759829352f205840eba1f6eb17613f9370b95 100644
--- a/ash/common/wm/overview/window_selector_item.h
+++ b/ash/common/wm/overview/window_selector_item.h
@@ -26,10 +26,6 @@ namespace views {
 class ImageButton;
 }
 
-namespace wm {
-class Shadow;
-}
-
 namespace ash {
 
 class WindowSelector;
@@ -198,9 +194,6 @@ class ASH_EXPORT WindowSelectorItem : public views::ButtonListener,
   // NOT_DRAWN layer since most of its surface is transparent.
   std::unique_ptr<views::Widget> item_widget_;
 
-  // Shadow around the item in overview.
-  std::unique_ptr<::wm::Shadow> shadow_;
-
   // Container view that owns a Button view covering the |transform_window_|.
   // That button serves as an event shield to receive all events such as clicks
   // targeting the |transform_window_| or the overview header above the window.