Use vector icon for Ash shelf launcher

ash/common/shelf/shelf_constants.h

Index: ash/common/shelf/shelf_constants.h
diff --git a/ash/common/shelf/shelf_constants.h b/ash/common/shelf/shelf_constants.h
index 632c095d9d8ef8e3bfb755ee848226cf1bda20ab..aa3caab1a19080cb8116a1aa1b4ca6c62d1aa5bb 100644
--- a/ash/common/shelf/shelf_constants.h
+++ b/ash/common/shelf/shelf_constants.h
@@ -36,6 +36,10 @@ ASH_EXPORT extern const int kTimeToSwitchBackgroundMs;
 // based on the desired shelf opacity level.
 ASH_EXPORT extern const SkColor kShelfBaseColor;
 
+// The foreground color of the icons used in the shelf (launcher,
+// notifications, etc).
+ASH_EXPORT extern const SkColor kShelfIconColor;
+
 // The direction of the focus cycling.
 enum CycleDirection { CYCLE_FORWARD, CYCLE_BACKWARD };