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

ash/common/shelf/shelf_constants.cc

Index: ash/common/shelf/shelf_constants.cc
diff --git a/ash/common/shelf/shelf_constants.cc b/ash/common/shelf/shelf_constants.cc
index 80aafcd1c7a250e6db6c9369567df6a3a792a018..c260855e5ef027af793f4791ded40593873d0a94 100644
--- a/ash/common/shelf/shelf_constants.cc
+++ b/ash/common/shelf/shelf_constants.cc
@@ -22,6 +22,8 @@ const SkColor kShelfInkDropBaseColor = SK_ColorWHITE;
 const float kShelfInkDropVisibleOpacity = 0.2f;
 const SkColor kShelfIconColor = SK_ColorWHITE;
 const int kShelfTranslucentAlpha = 153;
+const int kShelfTranslucentColorDarkenAlpha = 102;
+const int kShelfOpaqueColorDarkenAlpha = 230;
 const int kOverflowButtonSize = 32;
 const int kOverflowButtonCornerRadius = 2;
 const int kAppListButtonRadius = kOverflowButtonSize / 2;