[ash-md] Added darkness blending to the colorized shelf.

ash/common/shelf/shelf_constants.h

 // Copyright 2013 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_SHELF_SHELF_CONSTANTS_H_
 #define ASH_COMMON_SHELF_SHELF_CONSTANTS_H_
 
 #include "ash/ash_export.h"
 #include "third_party/skia/include/core/SkColor.h"
 
@@ skipping 43 matching lines @@
 // Opacity of the ink drop ripple for shelf items when the ripple is visible.
 extern const float kShelfInkDropVisibleOpacity;
 
 // The foreground color of the icons used in the shelf (launcher,
 // notifications, etc).
 ASH_EXPORT extern const SkColor kShelfIconColor;
 
 // The alpha value for the shelf background when a window is overlapping.
 ASH_EXPORT extern const int kShelfTranslucentAlpha;
 
+// The alpha value used to darken a colorized shelf when the shelf is
+// translucent.
+extern const int kShelfTranslucentColorDarkenAlpha;
+
+// The alpha vlaue usesd to darken a colorized shelf when the shelf is opaque.
+extern const int kShelfOpaqueColorDarkenAlpha;
+
 // The width and height of the material design overflow button.
 // TODO(tdanderson): Refactor constants which are common between the shelf
 // and the tray. See crbug.com/623987.
 extern const int kOverflowButtonSize;
 
 // The radius of the rounded corners of the overflow button.
 extern const int kOverflowButtonCornerRadius;
 
 // The radius of the circular material design app list button.
 extern const int kAppListButtonRadius;
 
 // The direction of the focus cycling.
 enum CycleDirection { CYCLE_FORWARD, CYCLE_BACKWARD };
 
 ASH_EXPORT int GetShelfConstant(ShelfConstant shelf_constant);
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_SHELF_SHELF_CONSTANTS_H_