Move Ash-specific vector icon files into a separate directory

ui/gfx/vector_icons/shelf_overview.icon

Index: ui/gfx/vector_icons/shelf_overview.icon
diff --git a/ui/gfx/vector_icons/shelf_overview.icon b/ui/gfx/vector_icons/shelf_overview.icon
deleted file mode 100644
index 5bfc8c88ce8f3b80f44d48477eb4b3f452171f12..0000000000000000000000000000000000000000
--- a/ui/gfx/vector_icons/shelf_overview.icon
+++ /dev/null
@@ -1,38 +0,0 @@
-// Copyright 2016 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.
-
-CANVAS_DIMENSIONS, 32,
-MOVE_TO, 4, 7,
-R_CUBIC_TO, -1.06f, 0, -2, 0.9f, -2, 2,
-R_V_LINE_TO, 14,
-R_CUBIC_TO, 0, 1.1f, 0.94f, 2, 2, 2,
-R_H_LINE_TO, 14,
-R_CUBIC_TO, 1.06f, 0, 2, -0.9f, 2, -2,
-V_LINE_TO, 9,
-R_CUBIC_TO, 0, -1.1f, -0.94f, -2, -2, -2,
-H_LINE_TO, 4,
-CLOSE,
-R_MOVE_TO, 13, 15,
-H_LINE_TO, 5,
-V_LINE_TO, 10,
-R_H_LINE_TO, 12,
-R_V_LINE_TO, 12,
-CLOSE,
-MOVE_TO, 22.88f, 25,
-CUBIC_TO, 24.05f, 25, 25, 24.1f, 25, 22.99f,
-V_LINE_TO, 9.01f,
-CUBIC_TO, 25, 7.9f, 24.05f, 7, 22.88f, 7,
-H_LINE_TO, 22,
-R_V_LINE_TO, 18,
-R_H_LINE_TO, 0.88f,
-CLOSE,
-MOVE_TO, 27.88f, 25,
-CUBIC_TO, 29.05f, 25, 30, 24.1f, 30, 22.99f,
-V_LINE_TO, 9.01f,
-CUBIC_TO, 30, 7.9f, 29.05f, 7, 27.88f, 7,
-H_LINE_TO, 27,
-R_V_LINE_TO, 18,
-R_H_LINE_TO, 0.88f,
-CLOSE,
-END