[Chrome OS MD] Draw a 1px separator between 2 tray items

ash/common/system/tray/tray_constants.h

Index: ash/common/system/tray/tray_constants.h
diff --git a/ash/common/system/tray/tray_constants.h b/ash/common/system/tray/tray_constants.h
index d29f3de669c44ecd9a66d2fbc5d4f3be1e8e27ff..4f098a9e7c8b646071dd119e2d06ed865ed07dbe 100644
--- a/ash/common/system/tray/tray_constants.h
+++ b/ash/common/system/tray/tray_constants.h
@@ -75,6 +75,12 @@ extern const int kTrayNotificationContentsWidth;
 
 extern const int kMessageCenterBubblePadding;
 
+extern const int kHitRegionPadding;
+
+// Color and width of a line used to separate tray items in the shelf.
+extern const SkColor kSeparatorColor;
+extern const int kSeparatorWidth;
+
 // The size and foreground color of the icons appearing in the material design
 // system tray.
 extern const int kTrayIconSize;