Sets the background color of shelf is opaque black when maximized (2nd)

ash/shelf/shelf_types.h

 // Copyright (c) 2012 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_SHELF_SHELF_TYPES_H_
 #define ASH_SHELF_SHELF_TYPES_H_
 
 namespace ash {
 
 enum ShelfAlignment {
@@ skipping 23 matching lines @@
 
   // Nothing is shown. Used for fullscreen windows.
   SHELF_HIDDEN,
 };
 
 enum ShelfAutoHideState {
   SHELF_AUTO_HIDE_SHOWN,
   SHELF_AUTO_HIDE_HIDDEN,
 };
 
+enum ShelfBackgroundType {
+  // The default transparent background.
+  SHELF_BACKGROUND_DEFAULT,
+
+  // The background when a window is overlapping.
+  SHELF_BACKGROUND_OVERLAP,
+
+  // The background when a window is maximized.
+  SHELF_BACKGROUND_MAXIMIZED,
+};
+
 }  // namespace ash
 
 #endif  // ASH_SHELF_SHELF_TYPES_H_